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PHYAN Exam 3


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How does the endocrine system influence cells?
by releasing hormones into the blood
What does the brain do other than regulate organ systems?(4)
-Integration of senses (sight, smell, hearing)
-Emotions, thoughts, memories, dreams
-able to devise complex technology
-is ignorant of itself (we have no idea how our brain works!)
What are the general fxns of the nervous system? (4)
-Sensory input
-Motor output
-Has ability to store experiences (memory) and learn
2 main divisions of Nervous System. . .
CNS - brain & spinal cord
PNS - everything else
2 divisions of PNS
-Sensory (afferent)
-Motor (efferent)
2 divisions of efferent
Somatic Nervous System
Autonomic Nervous System
2 divisions of Autonomic NS
Sympathetic NS
Parasympathetic NS
Another word for Sympathetic NS?
fight or flight
Another word for Parasympathetic NS?
rest and digest
What does the somatic division do?
conveys impulses to skeletal muscle

What does the autonomic division do?
carries impulses to smooth and cardiac muscles & glands

What is a neuroglial cell?
nonexcitable cell that supports, insulates and protects

reproduces throughout life

don't transmit electrical impulses
What is a neuron?
excitable nerve cells that recieve and transmit electrical impulses

What does a neuron depend on?
oxgenated blood supply

-can't store glycogen
-can't use anaerobic metabolism
Neurons have 2 common features, what are they?
-Cell body (soma)
-Processes (dendrites, axon)
What are the 2 common features of the neuron?
Cell body (soma)

Processes (dendrites & axon)
What is a soma?
an enlarged portion of the neuron containing the nucleus
What are processes of the neuron?
fibers extending from the cell body
-"recieving end" of neuron
-recieve signals from other neurons & transmits them to cell body
-neurons may have hundreds
-generates and transmits nerve impulses away from cell body
-neurons usually only have 1
-may be microscopic to 4 ft long
Distal end of axon branches profusely into
axonal terminals
when impulses reach axonal terminals they stimulate the release of chemicals called
neurotransmitters (secreted into extracellular space)
axon terminal is seperated from the next neuron or effector by
a tiny gap & synaptic cleft (neurons don't touch eachother)
the junction between neurons is called
a synapse
most axons are
white, fatty sheath covering axons
myelin sheath
what does the myelin sheath do?
-protects and insulates neurons from other neurons
-speeds transmission rate of nerve impulse
gaps in the myelin sheath r called
Nodes of Ranvier
myeling sheath around axons r destroyed; they become sclerotic (hardened & nonfunctional; ability to use muscles lost; autoimmune disease; PRO in myelin sheath is attacked; not curable
Multiple Sclerosis
What can help multiple scerosis?
oral doses of bovine myelin
a cluster of cell bodies in the CNS
a cluster of cell bodies in the PNS
cluster of fibers in the CNS
cluster of fibers in the PNS
cell body is damaged when cell body dies because
neurons don't go through cell division
a collection of myelinated fibers (a tract)
white matter
a collection of cell bodies & myelinated fibers
gray matter
a nerve impulse causes a
muscle action potential
what are the steps to a muscle action potential?
1) release of acetylcholine
-arrival of the acion potential causes exocytosis of synaptic cleft
-liberating Ach, which diffuses across cleft
2)Activation of Ach receptors
-Ach binds to its receptor
-Na+ channels in sarcolemma open and Na rushes into the muscle
3)Production of muscle action potential
-influx of Na+ causes depolarization of the muscle cell
-triggers a muscle action potential & contraction
4)Termination of Ach activity
-Ach is rapidly broken down by an enzyme called Acetylcholinesterase (AChE) which is present in the synaptic cleft
Several drugs & toxins block events in the . . .
Neuromuscular Junction (NMJ)
One of the most lethal chemicals known; produced by bacteria that proliferates in improperly canned foods; blocks exocytosis of synaptic vesicles at the NMJ; Ach isn't released, muscle contraction doesn't occur; tiny amts cause death by paralyzing the di
Butulinium Toxin
a plant derivative; is used by South American Indians on darts; binds to and blocks the Ach receptor but sarcolemma premeability to Na isn't changed; no influx of Na+, no muscle contraction; paralysis; often used during surgery to relax muscles
Which disease is derived from a plant?
Inhibits acetylcholinesterase; it slows removal of Ach from the synaptic cleft so more Ach is available to bind with receptors
Anticholinesterase agents
What do anticholinesterase agents do?
1) treats Myasthenia gravis
2) reversal of curare poisoning
what is a reflex arc?
the neural pathway over which a reflex occurs
Simple reflex arc
1) receptor
2) sensory (afferent) neuron
3) integration center (CNS)
4) motor (efferent) neuron
5) effector organ
when the reflux activates skeletal muscle it is a ________ reflex
when the reflux activates smooth or cardiac muscles or glands r activated it is a _______ reflex
autonomic (visceral) reflex
What r nerves?
-a bundle of nerve fibers (axons) w/ their CT wrappings
-found outside CNS
what is are mixed nerves?
both motory and sensory fibers
(they go both directions)
what do the nervous and endocrine systems do together?
they regulate functions of other body systems by chemical means
Hormones travel everywhere blood goes. . .what does that mean?
they're nonspecific
secrete their products through a duct onto a body surface; "secretions" NOT hormones; ex: mucous, seat, oil, saliva etc)
exocrine glands
r ductless, secrete hormones into surrounding tissure fluid; have a rich vascualr supply to recieve hormones
endocrine glands
What's a hormone?
a chemical messenger secretes into the extracellular fluid and then picked up by the blood
What do hormones do?
regulate the metabolic functions of he cells throughout the body
What r the 2 major types of hormone?
1) amino acid based hormones
2) steroid hormones
may be simple amino acid derivatives, peptides or PRO
amino acid based hormone
made from cholesterol; sex hormones (gonadal), the hormones produced by the adrenal cortex
steroid hormones
Hormones circulate through the blood but only affect certain tissue cells or organs called
target cells or target organs
the target cell/organ must have a specific PRO recepto for that hormone, either . . .
-on its plasma membrane
-in its interior
When hormone binds to its target it. . . .
alters the cells activity
What are the ways hormones change cell activity? (4)
1) changes in plasme membrane permeabilty or electrical state
2) synthesis of PRO or NZs in cell
3) activation/inactivation of NZs
4) stimulation of mitosis
Steroid Hormone Action
-diffuse through plasma membrane
-enter nucleus
-bind to specific receptor PRO
-hormone & receptor then bind to specific sites on DNA
-activates certain genes to transcribe mRna
-mRna moves to cytoplasm resulting in the synthesis of new PRO
Amino Acid Based Hormone Action
-bind to their specific recepto PRO in the plasma membrane
-this causes an NZ to be activated
-which catalyzes a Rxn that produces a 2nd messenger inside the cell
-causes additional intracellular changes
Blood levels of hormones are regulated by
Negative feedback mechanisms
3 types of stimuli that activate endocrine organs. . .
1) hormonal stimuli
2) humoral stimuli
3) neural stimuli
Hormonal Stimuli
-hormones from other gland stimulate an endocrine gland
-many hypothalamic hormones stimulate the pituitary
Humoral Stimuli
-changing blood levels of nutrients and some ions
-low blood Ca levels causes the parathyroid gland to secrete
Neural Stimuli
some endocrine glands r stimulated by nerves to secrete
What are the 2 hormones the hypthalamus synthesizes?
1) Oxytocin
2) Antidiuretic Hormone
Oxytocin and ADH hormone are stored and released from the
posterior lobe of the pituitary gland
Which hormone is only released during childbirth & in nursing women?
- Uterus (stimulates labor contractions)
- Breasts (initiates milk ejection)
The target organ for ADH is
the kidneys
pea-shaped gland hanging by a stalk from the hypothalamus; Suspended in the sella tursica of the sphenoid bone
Pituitary Gland
what does the posterior pituitary lobe do?
stores and releases hypothalamic homrones
-not a true gland b/c it doesn't synthesize hormones
What does the anterior pituitary lobe do?
synthesizes and secretes 6 hormones
-all r PRO
-all r regulated by hormonal stimuli & usually by neg. feedback
What r the 4 tropic hormones of the pituitary gland?
1) thyroid stimulating hormone (TSH) or Thyrotropin
2) Adrenocorticotropic Hormone (ACTH)
3) Follicle Stimulating Hormone (FSH)
4) Luteinizing Hormone (LH)
-Stimulates growth & activity of the thyroid
TSH - Thyroid Stimulating Hormone or thyrotropin
-Stimulates the adrenal cortex to release corticosteroids
ACTH - Adrenocorticotropic Hormone
-Stimulates te gonads (ovaries & testes)
FSH - Follicle Stimulating Hormone
What does FSH stimulate in the ovaries?
-Stimulates follicle maturation & ovulation
-follicle produces estrogen
What does FSH stimulate in the testes?
Sperm production
Luteinizing Hormones are
What does LH do for the ovaries?
-Promotes estrogen & progesterone production & secretion
What does LH do for teh testes?
-Stimulates testosterone secretion
Hyposecretion of Growth Hormone or Somatotropin during childhood causes. . .
Hypersecretion of GH or Somatotropin causes . . .
Hypersecretion of GH or Somatotropin in adults causes. . .
Hypersecretion of GH or Somatotropin usually results from
a tumor in the organ
What are the 2 non-tropin hormones in the pituitary gland?
1) growth Hormone (GH) or Somatotropin
2) Prolactin
What are the major targets of GH?
-Bones - long bone growth (epiphyseal plate)
-Skeletal muscles - increased muscle mass
What does prolactin stimulate?
milk production
When is prolactin stimulated?
secretes immediatley after child birth & while nursing
What does the thyroid gland secrete?
thyroid hormone
What kind of hormone are GH and Prolactin?
PRO hormones
what happens when you have hypthyroidism?
-physical/mental sluggishness
-low body temp

treatment - oral doses of thyroxin
What happens if you have hyperthyroidism?
-high metabolic rate
-weight loss
-nervous, agitated, hot
-rapid heart rate
What is the treatment for hyperthyroidism?
-removal of part of the thyroid
-administer radioactive iodine to destroy cells
Thyroid gland secretes. .
-thyroid hormone
Calcitonin is secreted in response to
-high blood Ca levels
-causes Ca to be deposited to bones
-may be diminished in the aged
Where is the parathyroid gland located?
behind the thyroid
Which hormone does the parathyroid secrete?
Parathyroid hormone
What does parathyroid hormone or parathormone do?
increases blood Ca levels
What does parathyroid hormone stimulate?
-osteoclasts to resorb bone & releas Ca to blood
-kidneys to inhibit urinary Ca excretion
-Intestinal cells to increase absorption of Ca
What is the inner region of the Adrenal glands called?
adrenal medulla
What is the outer region of the adrenal glands called?
adrenal cortex
The adrenal cortex stimulates how many steroid hormones?
-which are called corticosteroids
-derived from cholesterol
3 categories of coticosteroids
Mineralcorticoids are secreted when. . .
And stimulates. . .
Na blood level is low

stimulates kidneys
-promote Na retention
-increase water retention
-promotes K secretion
Principal hormone for mineralcoticoids is
Glucocorticoids are secreted. . .
In response to ACTH & to stress
-causes rise in blood levels of glucose and fatty acids
-encourages use of fats for NRG needs
-Saves glucose for brain
-anti-inflammatory effects
What r the principal hormones for glucocorticoids?
Gonadocorticoids are
weak sex hormones, mainly androgens
-amts. insignificant
Pancrea is located
below and behind the stomach
Endocrine cell clusters are called
Pancreatic islets
Pancreas secretes 5 pancreatic hormones but the 2 most important are:
Insulin is secreted by
Beta Cells
-in response to a "fed" state
-stimulates transport of glucose into cells
-lowers blood glucose
Glucagon is secreted by
Alpha cells
-in response to "fasting" state
-stimulates fat breakdown & release into the blood
-increase blood glucose levels
Steroid sex hormones are stimulated by
gonadotropic hormone from the anterior pituitary (FSH/LH)
Pineal Gland is located
in the center of the brain
Main secretion of pineal gland is
FXn unclear
blood levels peak at night
-large in children, shrinks as we age
Thymus gland is located under
the sternum
-large in children & reduces with age
The main hormone secreted by the thymus is
Thymosin is
essential for normal immune response
-regulates activation of T lymphocytes (disease fighting blood cells)
According to structure what are the 3 types of neurons?
According to FXN, what are the 3 types of neurons?
Neurons are:
-irritable (rspond to a stimulus)
-conductive (conduct electrical impulse down the axon
-secretory (secrete chemicals)
saltatory conduction is when
action potentials jump over myelin (node to node)
When axons are unmyelinated it makes conduction
much slower
Skeletal muscles must be
-stimulated by a motor neuron
the NMJ synapse is between
a somatic motor neuron & muscle fiber
Axon terminal contains
tiny synaptic vesicles
-membrane-bound sacs
-contain the neurotransmitter
The neurotransmitter at the NMJ is
What does the adrenal medulla secrete?
epinephrine and noneepinephrine
What do epinephrine and nonepinephrine do?
-increse blood glucose levels
-increse heart rate
-blood vessels constrict, diveting blood from nonessential organs TObrain, heart & skeletal muscle

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