Autonomic and Endocrine

Question 1

Describe the physical division of the nervous system and the structures involved in each division

Answer 1

It is split into a CNS and PNS. CNS is made of the brain and spinal cord. PNS includes all nervous tissue outside CNS including spinal nerves, cranial nerves, Ganglia and peripheral nerves

Question 2

Describe the functional division of the nervous system as a whole

Answer 2

The CNS responds to incoming sensory information (afferent neurons) from PNS. It sends motor (efferent neurons) through cranial and spinal nerves to PNS. PNS is divided into the Somatic NS, Autonomic NS and Enteric NS.

Question 3

Compare the SNS and ANS in terms of sensory input, control of output, motor neuron pathway, neurotransmitters and effectors

Answer 3

SNS inputs special sensory information and normal somatic senses. Whereas ANS uses interoceptors in visceral organs monitoring internal conditions that are less consciously felt.
SNS is under voluntary motor control from cerebral cortex whereas ANS is involuntary from the limbic system, hypothalamus, brainstem and spinal cord.
SNS has a specific one neuron pathway, whereas ANS has 2 neuron pathway that is more simultaneous.
SNS uses ACh only for excitement, whereas ANS uses ACh and Norepinephrine depending on the division. - – SNS Effector tissue is skeletal muscle whereas ANS effector tissues are smooth muscle, cardiac muscle and glands. Both are innervated by CNS

Question 4

Describe the Enteric nervous system- sensory receptors, effector tissues - under involuntary control

Answer 4

Sensory neurons monitor chemical changes in GI tract as well as wall stretching. Enteric motor neurons are in Enteric plexuses communicate with CNS through ANS but generally independent. They govern contractions, secretions and activities of endocrine cells in effector tissue (smooth muscle, glands and endocrine cells of GI tract).

Question 5

What is the broad purpose of the Nervous System

Answer 5

A system of communication to allow us to coordinate our actions and bodily functions to adapt to a changing environment. Sensory, integrative and Motor.

Question 6

Describe the features of transmission of impulses from one nerve to another (synapse)

Answer 6

Dendrites have numerous receptor sites for binding chemical messengers from other cells. AP travels from the cell body down the long axon to the synaptic end bulb of axon terminals. This causes a change in shape in voltage gated Ca2+ channels allowing Ca2+ to enter. Ca2+ causes synaptic vesicles containing neurotransmitter to fuse with the cell membrane so it can cross the synaptic cleft and bind to ligand gated ion channel on the post synaptic neuron. This makes a shape change that allows Na+ to enter the post synaptic neuron and depolarise-> AP.

Question 7

What is the difference between myelinated and unmyelinated nerve fibres in the PNS

Answer 7

Both axons are covered by Schwann cells however for myelinated, One schwann cell can produce the myelin sheath for one axon by spiralling many times around the axon- the glial membrane layers becoming the myelin.But in unmyelinated On Schwann cell can enclose 20 or more unmyelinated axons

Question 8

What are the neurotransmitters associated with the sympathetic and parasympathetic divisions respectively

Answer 8

Sympathetic and Parasympathetic divisions use ACh for the first synapse between the preganglionic neuron and postganglionic neuron at the ganglion, however for Sympathetic division to most effector tissues it uses Norepinephrine whereas Parasympathetic uses ACh. There is an exception in Sympathetic where sweat glands also use ACh

Question 9

What are the features of the alarm response and which division is responsible for it

Answer 9

Sympathetic induces the alarm response: exercise, emotion and excitement. This causes

Increased rate of contraction of heart, constriction of vessels , esp in skin-> increased blood pressure - can send nutrients where its needed
Water retention - preserve body fluid volume in case of bleeding.
Dilation of pupils (more aware)
Decreased salivation, digestion
Dilation of bronchi- more oxygen, breathe faster
increased blood sugar
contraction of arrector pilli muscles and increased sweat.

Question 10

What are the features of the relaxation response and which division is responsible for it

Answer 10

Parasympathetic division induces relaxation response: repletion, rest and relaxation.

Decreased rate and force of contraction
Contraction of pupils
Increased salivation, digestion
Constriction of bronchi- slower breathing
Dilation of peripheral blood vessels- more blood to peripheries- warmth.

Question 11

Describe the locations of endocrine glands in the body

Answer 11

in the brain: Hypothalamus (triangle under thalamus), pineal and Pituitary glands
in the thoraic cavity: Thyroid on the trachea, Thymus on the heart
in the abdominal cavity: Liver on top right, Adrenal glands on the top of the kidneys
in the pelvic area: testes and ovaries

Question 12

Compare function/ location of circulating hormones vs local hormones

Answer 12

Circulating hormones are made by endocrine cells which produce hormone which circulates in blood to reach distant target cells through capillaries - can linger. Whereas Local hormones are inactivated quickly, Paracrine cells act on neighbouring cells and Autocrines act on the same cell.

Question 13

Describe the control of hormone release - how is it an inducible system

Answer 13

First the organ is triggered to synthesise, store and release hormone only when needed. Then it circulates in the blood and reaches target tissues. It will only induce a response if the target tissues have the correct receptor. As part of response, target tissues can release something that is detected by the organ as a negative feedback signal to switch off the production of the hormone. As the hormone is circulating, it also has breakdown or excretion to turn it off as well.

Question 14

Describe the transport for Lipid soluble hormones (steroid and thyroid hormones) in the blood vs Water soluble

Answer 14

Lipid soluble hormones are bound to a transport protein made by the liver. They temporarily increase the solubility of the LSh in blood. Retard the passage of small hormones through filtering mechanism of the kidney therefore reduce loss in urine. Provide a ready reserve of hormone in the blood stream releasing a small fraction of hormones to be free when needed.
Water soluble are just in free form.

Question 15

Describe the mechanism of Action of Lipid soluble hormones

Answer 15

LSh diffuses through blood, interstitial fluid into the cell to the nucleus
hormone binds to receptors located within cytosol or nucleus. The activated receptor hormone complex then alters gene expression; turning genes on or off.
newly formed mRNA directs synthesis of specific proteins on ribosomes. (enzymes possibly)
New protein alters cell activity and causes response typical of that hormone.

Question 16

Describe the mechanism of Action of Water soluble hormones

Answer 16

Hormone binds to receptor on plasma membrane of target cell which activates G protein which activates Adenyl cyclase
Activated adenyl cyclase converts ATP to cAMP which is 2nd messenger to activate protein kinases
Activated protein kinases phosphorylate other enzymes in a cascade.
Phosphorylated enzymes catalyse reactions that produce physiological response. Or phosphorylation can turn off enzymes
After a brief period phosphodiesterase inactivates cAMP which turns off cell response unless new hormone molecules come

Question 17

Explain the relationship between the hypothalamus and pituitary glands in number of hormones secreted by the two

Answer 17

The hypothalamus produces 9 hormones which are releasing or inhibiting hormones to control the pituitary.
The pituitary itself then can produce 7 hormones which enter the bloodstream to control the other endocrine organs to produce their own hormones which act more locally.

Question 18

What does the hypothalamus pituitary Axis regulate

Answer 18

They regulate growth, development, metabolism and homeostasis

Question 19

How does hormones produced in the hypothalamus travel to the pituitary

Answer 19

Hypothalamic neurosecretory cells get triggered to release hormones through the termini at the end of their axons which are close to their capillary network at the base of the hypothalamus.
Hormones travel through hypophyseal portal vein through secondary plexus to capillaries sitting on the anterior pituitary to then go to target cells in the pituitary.

Question 20

Describe the structure and location of the adrenal gland

Answer 20

ONe adrenal gland sits on top of each kidney. They have an outer capsule, with a cortex and then middle core called medulla.

Question 21

Compare the hormones are released by the Adrenal medulla with the Adrenal cortex

Answer 21

Medulla cells (modified post ganglionic “neurons (without axons)) secrete Epinephrine and Norepinephrine into the blood stream.

Whereas Adrenal cortex secrete mineralocorticoids and glucocorticoids

Question 22

What are the two stages of the Stress Response

Answer 22

ALARM response: Sympathetic autonomic activation: mobilise resources for immediate physical activity, get more oxygen and glucose into circulation, increase alertness and activity leading to fight or flight, Followed by Sympathetic activation of the Adrenal medulla (through ACh) which secretes epinephrine and norepinephrine into the blood to supplement and prolong the alarm response

2nd stage: (Resistance reaction) Stimulation of the adrenal cortex to produce cortisol (from CRH in hypothalamus -> ACTH from anterior pituitary) that helps to dampen inflammation, depress immune response to change balance to favour immediate tissue repair to reduce tissue damage if we get damage.

Question 23

What stimulates the adrenal medulla

Answer 23

Adrenal medulla is stimulated by sympathetic preganglionic neurons which release AcH at the synapse to the modified post ganglionic “neurons” acting as secretory cells in the medulla

Question 24

What is the effect of Norepinephine + Epinephrine

Answer 24

The effect is to act on the tissues already stimulated by the autonomic system as to enhance/ Sustain the sympathetic autonomic alarm response.

Question 25

What is the effect of mineralocorticoids

Answer 25

Mineralocorticoids increase Na+ conc and water and decrease K+ conc in the blood. This leads to increased blood volume and pressure.

Question 26

What stimulates the production of mineralocorticoids at the Adrenal cortex

Answer 26

Increased K+ concentration or Angiotensin 2 in the blood

Question 27

What stimulates the production of glucocorticoids at the Adrenal cortex

Answer 27

AdrenoCorticoTropinHormone (ACTH) made from the pituitary that was released into the blood stream. The hypothalamus told the pituitary to do this by releasing Corticotropin ReleasingHormone (CRH) into the primary hypophyseal plexus and then portal vein to the anterior pituitary.

Question 28

Give an example of a mineralocorticoid and glucocorticoid

Answer 28

mineralocorticoid: Aldosterone
glucocorticoid: Cortisol

Question 29

What is the effect of glucocorticoids

Answer 29

It does the resistance reaction to stress-

increases glucose, fatty acids, and amino acids
dampens inflammation
It alters the balance of other immune responses changing the balance of B and T cells to deal with short term cuts and infection (suppresses immune response)
sensitises vessels to vasoconstriction

Question 29

What are the 6 specific physiological reactions of the resistance reaction- actions of Coritsol- a glucocorticoid

Answer 29

Protein breakdown (in muscles) = allowing amino acids available for rebuilding of damaged tissue/ ATP production
Gluconeogenesis in the liver from amino acids/ lactic acids = glucose for ATP production
Lipolysis= breakdown of triglyceride and fatty acids can be used to build membranes
Vasoconstriction= vessels more sensitive to hormones that cause vasoconstriction leading to rise in blood pressure.
Anti-inflammatory= inhibiting white cells to limit tissue damage done by them. Also means slower wound healing
Immune depression, using the energy for other things, but then this leads to increased susceptibility to some infections

Question 30

what are the negative feedback controls of the cortisol release from adrenal cortex

Answer 30

Elevated cortisol levels inhibit the release of ACTH by anterior pituitary corticotrophs
Elevated cortisol inhibits the release of CRH by hypothalamic neurosecretory cells/

Question 31

What is the difference between Eustress and Distress

Answer 31

Eustress is acute - it prepares us to meet certain challenges so helpful/beneficial. Distress is chronic- it is associated with undesirable events that is potentially harmful due to activation from mental triggers.

Question 32

What is some consequence of habitually hostile people / stress cardiomyopathy syndrome

Answer 32

Chronic activation of the sympathetic ns, increasing blood pressure and cardiac output as well as more vasoconstriction of capillaries which leads to greater risk of cardiac infarct (heart attack)