Wednesday, June 20, 2012

Biological Science 7 (Nervous and Endocrine Systems)

Nervous and Endocrine Systems

Day 12:

Nervous and Endocrine Systems:

Nervous System
Thank You Sebastian Kaulizki

The nervous system is the control center of the body, but the endocrine system can effect the nervous system (as can all the other systems). The way nerves receive lots of feedback and decide what to transmit, the whole body too, receives signals from not only the nervous system, but indirectly through all the systems. The body is a whole, made of physical, mental and emotional components. Speaking of humans in physical terms is normal in medicine, but metal changes to an individual have physical effects too, as do emotional changes. Recent studies have been done for psych medications, where the placebo has been better then the medication at treating depression. This puts the chemical imbalance theory on thin ice. I think tension and stress cause depression. I think little traumatic events are like splinters, that some people don't want to deal with since they are tender, the little splinter becomes an infection, the infection becomes sepsis... there really is no limit to how big a small problem that never gets fixed can become. Yoga, a healthy family life, healthy food, martial arts and normal exercise are the best ways I know to reduce stress, not surprisingly none of those are common things in America. I hope that changes. Both diabetes and obesity are diseases of the endocrine system, making it extremely relevant since 47.7% of Americans are obese, 8.3% of Americans have diabetes. Greater research, understanding and application of new knowledge of the endocrine system will be instrumental in helping stem the tide of this sea of illness. 

A. Endocrine System: Hormones

The endocrine system is made of various glands including the heart (which secretes hormones), the hypothalamus, the pineal gland, the thyroid gland, the parathyroid gland, the adrenal gland, the islets of Langerhans, the ovaries and the testis, which all secrete hormones sending signal to help regulate the body.

The Endocrine System is Probably the Basis for the Chakras

1. Function of Endocrine System (Specific Chemical Control at Cell, Tissue, and Organ Levels)
The endocrine system makes hormones that control cells, tissues and organs chemically. The endocrine system is heavily tied into homeostasis and immune function.

2. Definitions of Endocrine Gland, Hormone
Endo: within.
Crine: to secrete.
Endocrine: secrete things within the body (opposite of exocrine: secretes tears and sweat).
Hormone: chemicals that travel through the body and regulate cell function or metabolism.

3. Major Endocrine Glands (Names, Locations, Products)
Hypothalamus (mainly regulates the pituitary) is located just above the brain stem. Releasing Hormones cause the pituitary to release hormones.
  • Oxytocin (the hormone of love, milk secretion and stop a mother from bleeding)
  • Antidiuretic Hormone (ADH) AKA Vasopressin (urinate less, higher blood pressure)
  • Prolactin Releasing Hormone (PRH) (release Prolactin)
  • Corticotropin Releasing Factor (CRF) (release ACTH)
  • Thyroid Releasing Hormone (TRH) (release Thyroid)
  • Growth Hormone Releasing Hormone (GHRH) (release Growth Hormone)
  • Gonadotropin Releasing Hormone (GnRH) (release FSH and LH)
Pineal Gland (pine cone shaped, the size of a grain of rice) is located near the center of the brain, mid-line, tucked into a groove where the two rounded thalamic bodies join.
  • Melatonin (regulates sleep)
  • Adrenoglomerulotropin (causes the adrenal cortex to produce aldosterone)
  • Possibly Dimethyltryptamine (DMT) (creates dreams) 
Pituitary Gland (the anterior pituitary glad stores and releases the oxytocin and antidiuretic hormone produced by the posterior lobe of the pituitary and hypothalamus, the size of a pea) located, not in the brain but it is near the hypothalamus.

Regulated by the hypothalamus' hormones:
  • Prolactin (PRL) (lactation)
  • Thyroid Stimulating Hormone (TSH) (increase metabolism)
  • Growth Hormone (GH) (growth of muscle and bone, consumes fat)
  • Follicle Stimulating Hormone (FSH) (production of sperm and ovary follicles) 
  • Lutenizing Hormone (LH) (production of testosterone in testis and ovulation)
  • Melanocyte Stimulating Hormone (MSH) (produces melanocytes in skin and hair, sexual arousal in the brain)
  • Adrenocorticotropic Hormone (ACTH) (release glucocorticoids and mineralocorticoids in the adrenal cortex)
Thyroid (increase metabolism) below the adam's apple on the neck, near the collar bone.
  • Calcitonin (takes calcium into the bones, out of the blood)
  • Thyroxine and Triiodothyronine (increase heart rate, cardiac output, breathing, metabolic rate, sympathetic activity, endometrium growth)
Parathyroid Glands (calcium into the kidneys and blood, there are 4, each is the size of a grain of rice) they are behind the thyroid anywhere from the jaw to the chest.
  • Parathyroid Hormone (PTH) (increases blood and kidney calcium, decreases bone calcium, causes dietary calcium absorption).
The Parathyroid is Behind the Thyroid Only 85% of the Time

Thymus (stimulates T cells) located just above the heart.
  • Thymic Factor (TF) (pain killer, anti-inflammatory, causes T-cell differentiation, produces interleukin-6 in the spleen)
  • Thymosin (causes T-call maturation, stimulates LH and GnRH (in vivo), PRL, GH and ACTH (in vitro).
  • Thymic Humoral Factor (THF) (possibly antiviral, stimulates production of interleukin-2)
  • Thymopoietin (causes T-cell differentiation, enhances function of mature T-lymphocytes)
Heart (size of a fist, increasingly considered part of the endocrine system) located in the chest, behind the sternum 99% on the left side, rarely on the right side (dextrocardia).
  • Atrial Natriuretic Peptide (ANP) (vasodilator, controls water, sodium, potassium and fat, reduces blood pressure)
  • Brain Natriuretic Peptide (BNP) (vasodilator, responds to stretching of heart muscle).
  • Cardiac Natriuretic Peptide (CNP) (inhibits hypertrophy of cardiomyocytes).
Adrenal Glands specifically the medulla (activate the sympathetic nervous system, the left is a crescent shape, the right is a triangle shape) located on top of and behind the kidneys.
  • Epinephrine (adrenaline) (cause sympathetic nervous response, increases heart rate, respiratory rate, vasoconstrictor or vasodilator, muscle contraction, causes glycogenolysis).
  • Norepinephrine (noradrenaline) (sympathetic nervous response, suppresses neuroinflammation, affects the amygdala).
Pancreas (nearly six inches long) located across the back of the abdomen, behind the stomach, connected to the duodenum by the pancreatic duct, mostly on the left side.
  • Growth Hormone Inhibiting Factor (GHIF) (stops adults from growing)
  • Insulin (decrease blood sugar, stimulates glucose by uptake into cells)
  • Glucagon (increases blood sugar, stimulate gluconeogenesis, break down glycogen)
Ovaries (regulate ovulation and egg development) located 2-3 fingers breath inside the hip bones.
  • Estrogen (stimulates breast cells, salt and fluid retention, many changes related to the menstrual cycle)
  • Progesterone (binds with the same receptors and blocks mineralocorticoidsteroids including aldosterone, cortisol and corticosterone, causes many changes related to pregnancy)
  • Testosterone (a small amount is produced in the ovaries)
Testis (mainly produce testosterone) located in the scrotum, males only (were once ovaries, that migrated). 
  • Testosterone (produce body hair, muscle, increase bone mass, prevent osteoporosis, 8 times more in males).

Learn More Details: <- Comparing Estrogen/Progesterone <- Review Game for All Hormones :)

4. Major Types of Hormones
Amino Acid Based: amnio acid derivatives (most sterioids).
Steroids: cholesterol derivatives (testosterone, estrogen and adrenocortical hormones).

B. Endocrine System: Mechanisms of Hormone Action
Hormones can be water soluble or lipid soluble. Water soluble hormones can not enter the cell and need a receptor; lipid soluble hormones directly activate genes within the cell.

1. Cellular Mechanisms of Hormone Action
  • Water soluble hormones bind to a receptor on the cell membrane and a secondary messenger relays the signal inside the cell.
  • Lipid soluble hormones cross the membrane and activate genes inside the cell.
  • Steroid pathway: bind to receptors inside the cell inside or outside the nucleus, affecting the amount of mRNA and proteins produced.

The Steroid Pathway
McGraw Hill

  • cAMP pathway: amino acid hormones bind to receptors in the membrane, the G protein is activated, adenylate cyclase is activated, cAMP is made causeing a protein kinase cascade.
Please Let me know if there is a better video of the cAMP pathway...
cAMP Pathway Video (No Audio)

  • Phospholopid pathway: amino acid hormone binds to membrane receptor, a G protein is activated, phospholipase C is activated, membrane phospholipids split into DAG and IP3, DAG triggers a protein kinase cascade, IP3 releases Ca 2+ from ER.

Please Let me know if there is a better video of the phospholipid pathway...

Phospholipid Pathway (No Audio)

2. Transport of Hormones (Bloodstream)
Hormones can travel long distances in the bloodstream to affect far parts of the body.

3. Specificity of Hormones (Target Tissue)
Hormones only have receptors on cells they affect. The cells can reduce or increase the amount of receptors they have on their membrane.

Day 13:

4. Integration with Nervous System (Feedback Control)
The nervous system can regulate hormones being produced in the hypothalamus that in turn regulate other hormones. 

Humoral control: glands respond to chemical levels in the blood (low blood calcium)
Neural control: glands respond to nerve stimulus (stress response)
Hormonal control: glands are stimulated by other hormones (tropic hormones)

C. Nervous System: Structure and Function

Bones are the simplest: there are 206 bones in the body. Muscles are needed to pull bones in multiple directions: there are several billion muscles (nearly 700 skeletal, 1 cardiac, several million arrector pilli and several billion smooth muscles cells). Nerves are needed to control and receive multiple signals (pain, pressure, heat, cold, location in space, stretch) from all those bones and muscles: there are over 7 trillion nerves in the human body (12 cranial nerves, 32 pairs, 214 named nerves). The nervous system of a human is immensely complex. We have duplicates of memories, we have plasticity to our brain and sentience. It may be necessarily to look at one piece at a time to understand the nervous system, however in reality it functions as a whole that is more then the additions of its parts.

1. Major Functions
Response to stimulus (pressure, pain, temperature), sensory/afferent (hearing, smelling, tasting, feeling, positional awareness, sight), fine control of the body/efferent and integration of the body systems (movement, digestion, cellular functions, hormone regulation), cognitive abilities (language, awareness, interpretation, pattern recognition, memory recall). Just about everything...

A. High-Level Control and Integration of Body Systems
Higher regulatory systems refer to non-homeostatic pathways. High level of control of the body usually refers to fine motion control, like professional dancers or athletes exhibit. High-level control and integration of body systems can be described by the bodies ability to perform homeostasis keeping the body within a few degrees of the ideal temperature, the bodies ability to perform complex tasks or the way that the body systems always work together to preform biological tasks that keep the body alive and well.

B. Response to External Influences
Pressure and vibration are sensed by mechanoreceptors (Meissner corpuscles, Merkel disks, Ruffini corpuscles and Pacinian corpuscles). Pain is sensed by nociceptors. Temperture extreems are sensed by thermoreceptos. Chemicals are sensed by chemoreceptors. Light is sensed by photoreceptors. Osmotic pressure changes are sensed by osmoreceptors. Position is sensed by proprioceptors. Afferent nerves tell the brain what is going on and efferent nerves carry responses such as movement.

C. Sensory Input
Afferent nerve impulses convey messeges to the CNS, including special senses such as hearing, sight, taste, feeling, smell as well as simple input such as pressure, temperature, pain and position.

D. Integrative and Cognitive Abilities
Dr. Pascale Michelon describes cognitive abilities: 
"Cognitive abilities are the brain-based skills needed to carry out a task. They have more to do with the mechanisms of how we learn, remember, problem-solve, and pay attention rather than with any actual knowledge." 

List of Cognitive Abilities: 
Perception: recognition and interpretation 
Attention: sustained concentration
Memory: short or long term memory
Motor: ability to move, ability to manipulate objects
Language: hearing and speaking in a meaningful way
Visual and Spacial Processing: ability to process images, distance/spacing, visualization
Executive Functions: goal and plans, flexibility, insight into other people, anticipation/prediction, problem solving, decision making, working memory, emotional control, sequencing/ordering tasks by priority, inhibition/self control

Notice the MCAT tests almost all your executive functions. Sharp Brains has techniques you can use to practice your cognitive skills, if you know which ones need work.

2. Organization of Vertebrate Nervous System
The central nervous system is the brain and spinal cord (everything near the vertebrae). The peripheral nervous system goes away from (efferent) or to (afferent) the vertebrae/spinal cord from the rest of the body. Motor (efferent) nerves can be somatic/voluntary (for skeletal muscles) or autonomic/involuntary (for organs). The autonomic nervous system has a sympathetic division (fight or flight, wake up) and a parasympathetic division (rest or digest, go to sleep). 

3. Sensor and Effector Neurons
Sensor neurons are afferent going to the brain, from the body. A sensor feels
Effector neurons are efferent going to the body, from the brain. Movement takes effort.

4. Sympathetic and Parasympathetic Nervous Systems (Functions, Antagonistic Control)
Sympathetic vs Parasympathetic Nervous System:
Increased heart rate/Decreased heart rate
Increased blood pressure/Decreased blood pressure
Increase blood flow to muscles/Decreased blood flow to muscles
Decreased blood flow to digestion/Increased blood flow to digestion
Pupil dilation/Pupil constriction
Break down glycogen to use/Synthesizes glycogen for storage

5. Reflexes
A reflex is a response to a stimulus that bypasses your brain for speed. Ex. Removing your hand from a hot stove. The burning feeling gets to your spine, and the impulse to remove your hand is sent back (without waiting for the burning signal to get to the brain).

A. Feedback Loop, Reflex Arc, Effects on Flexor and Extensor Muscles
A classic feedback loop is the yin/yang relationship. Yang chases yin and yin follows yang.


Even simpler feedback loop, two parts are effecting each other:
A effects B, B effects A

A feedback loop is the path, from the time of detection of any issue, to the modification of the issue. A negative feedback loop slows a process down. Ex. If you are too cold, negative feedback slows down your cooling by constricting the blood vessels on your extremities. Positive feedback accelerates a process. Ex. Blood clotting, when you are cut the presence of some clotting factors triggers more clotting to occur.

A reflex arc can be withdraw from a painful stimulus such as a tap on the patellar tendon.

The details of a reflex arc: the receptor sends a message to a sensory neuron, which sends the signal to the integration center (CNS), which sends the signal to a motor neuron, which sends the signal to an effector (usually a muscle). Monosynaptic loops have no interneuron, polysynaptic loops do have an interneuron (a neuron between the sensory and motor neuron). The reflex arc causes opposite actions on flexor and extensor muscles. If the extensor contracts the flexor relaxes.

B. Roles of Spinal Cord, Brain
Spinal cord provides the signal (synapse) to respond to the reflex arc. The brain is aware, although not involved in sending the signal (synapse).

C. Efferent Control
Your brain can choose to override spinal reflexes. A simple example is training the eye not the close when an eyeliner pencil comes near it. Another one is not flinching at loud gun shots at the firing range.

D. Nervous System: Sensory Reception and Processing

Sensory comes in a myriad variety of forms and the brain processes the nerve impulses to come to an interpretation of what is going on...

1. Skin, Proprioceptive and Somatic Sensors

  • Skin Sensors: light (Meissner's corpuscles, Merkel disks/nerve endings) and deep pressure (Pacinian corpuscles), sustained pressure (ruffini endings), cool (C-fibers and thinly myelinated A delta fibers) and warm temperature (unmyelinated C-fibers), sharp (Aδ fiber axons) and dull pain (C fiber axons).
  • Proprioceptive Sensors: position of the body. Located in the muscle (muscle spindle fibers) and connective tissue (Golgi bodies).
  • Somatic Sensors: touch and pressure (mechanoreceptors), temperature change (thermoreceptors) and pain (nocioreceptors). These are the primitive senses compared to the advanced senses of taste, scent, vision and hearing.

2. Olfaction, Taste
Olfaction (smell) and taste both use chemoreceptors. During olfaction chemicals enter the nostrils and nasal cavity, where they are trapped on mucus and picked up by cilia on receptors that send a signal via depolarization that transducers the signal to the brain. So in essence, you get small pieces of rose stuck in your nose hairs, and your hairs give your brain the rose smell signal. Kind of gross if it isn't a good smell... During taste chemicals dissolve in saliva, they enter a taste bud, mircrovilli of the cells catch the chemicals and the cell sends out a signal to the brain. A significant portion of perceived taste is actually olfaction. When olfaction is blocked by a stuffy nose, people are able to taste the true taste of food.

Summary of How Taste and Smell Interact

3. Hearing
Hearing is caused by vibrations being translated into nerve signals that are translated into sound by the brain.

A. Ear Structure
The outer ear (pinna) has an auricle which extends from the lobule to the superior part of the helix. The external auditory canal leads to the tympanic membrane (ear drum). The middle ear begins at the ear drum, the auditory ossicles (malleus/hammer, incus/anvil and stapes/stirrup) transmit vibrations into the oval window of the vestibule and then into the choclea (with hair cells that send signals to the brain).

The Structure of the Ear

B. Mechanism of Hearing
Vibrations enter the ear, travel down the ossicles (hammer, anvil, stirrup) into the cochlea of the vestibule where the vibrations excite hair on receptor cells that send signals to the brain.

 Mechanism of Hearing Video

4. Vision
Vision dominates the senses in most people. It is taken for granted how much we rely on vision and also how much people who are blind can do without it. Two of my good friends are blind. One has a thriving business, the other plays piano, sings, excels at academics and both fight successfully in martial arts tournaments. Vision is no more real then any of the other senses. The brain helps create much of what we see. 

René Descartes highlighted several ways human vision is systematically prone to error

A. Light Receptors
At the back of the retina are rods (sense light and dark) and cones (sense color in bright lighting). 

Rhodopsin is the chemical responsible for light reaction, light converts cis-retinal to trans-retinal, which causes hyperpolarization of the photoreceptor cell (sending a signal to the brain via the optic nerve.

The Light Receptors of the Retina

B. Eye Structure
Light travels trough the cornea, is filtered by the pupil, hits the lens (focusing light on the retina where the photoreceptors are located). Tears are aqueous humor, inner eye fluid is vitreous humor.

Eye Structure

C. Visual Image Processing
The lens of the eye forms a real image on the retina (real images are upside down). The brain flips the image right side up, also combining both eyes into one 3D image with depth and eliminating the blind spot from each eye.

Review of Vision and Visual Image Processing

1 comment:

  1. Thank you for this organized guide. This is incredibly helpful as I study for the Bio section for the MCAT! Happy studying!