Autonomous and Endocrine

Question 1

Divisions of the Peripheral Nervous System

Answer 1

Receives sensory input from afferent sensory neurons.
Sends out impulses through efferent motor neurons.
Motor neurons separated into the autonomic and somatic nervous systems.
SNS responsible for skeletal muscle and voluntary movement.
ANS responsible for involuntary actions involving cardiac/smooth muscle and glands.
ANS splits into the sympathetic and parasympathetic systems.
Sympathetic is involved in the alarm response while parasympathetic is involved in the relaxation response.

Question 2

Autonomous nervous pathway

Answer 2

CNS–> Ganglion–> Effector
The motor impulse originates in a CNS structure such as the limbic system, hypothalamus, spinal cord or brain stem.
The ganglion is a switching station, as ANS responses tend to be body-wide and affect many effectors, so there must be multiple postganglionic neurons for them.
The adrenal gland classifies as a ganglion.
Preganglionic neurons tend to be myelinated, while postganglionic neurons are not.

Question 3

Role of acetylcholine in the ANS.

Answer 3

Used by the preganglionic neurons in both sympathetic and parasympathetic divisions.
Also found in all parasympathetic postganglionic neurons and postganglionic sympathetic neurons to sweat glands.

Question 4

Difference between autonomous and somatic sensory

Answer 4

ANS: Uses interoceptors to monitor internal environment. Impulses from these stimuli never reach cerebral cortex so is never registered consciously.
SNS: Uses chemoreceptors and mechanoreceptors to detect somatosensory stimuli. Impulses from these reach the somatosensory cortex and are therefore registered consciously.

Question 5

Role of norephinephrine/catecholamines in ANS

Also the nature of the receptors they bind to

Answer 5

Used by postganglionic neurons in the sympathetic nervous system.
Receptors are alpha 1,2 or beta 1,2 and 3 and are found on visceral effectors or brown adipose tissue (b3)
a1 & b1: Excitatory
a2 & b2: Inhibitory
b3: thermogenesis.
Broken down by the action of COMT/monoamine oxidase.

Question 6

Functions of acetylcholine receptors

Answer 6

Muscarinic: Found on visceral effectors. Generally has an inhibitory function and cause muscle relaxation (normally when under parasympathetic innervation), such as in vessel dilation.
Nicotinic: Found on dendrites and cell bodies of postganglionic neurons, chromaffin cells of the adrenal medulla and the motor end plate.
Causes muscle contraction and release of epinephrine,

Question 7

Raynaud’s Disease

Answer 7

Chronic overactivation of the sympathetic nervous system. Causes the smooth muscle around capillaries to constrict and prevent blood flow to extremities-ischemia.

Question 8

Effect of the Stress Response (Alarm and Resistance)

Answer 8

Alarm (FoF response):
5x higher rate and strength of heart contractions.
Dilation of pupils to allow more visual stimulus intake.
Dilation of bronchi
Constriction of capillaries under the skin.
Contraction of arrector pili to raise hairs.
Increased sweat production (cholinergic)
Increased glycogenolysis
Increased water retention and blood pressure.
Reduced digestive function.

Resistance:
Increased lipolysis (liver-hCG) and gluconeogenesis. (Cortisol)
Increased breakdown of proteins for tissue repair. (Cortisol)
Reduced inflammation. (Cortisol)
Dampened immune response.
Increased sensitivity of vessels to signals of vasoconstriction (Cortisol)
Increased glycogenolysis (liver-hCG).
Increased rate of metabolism (thyroid-TSH)

Question 9

Effect of the Relaxation Response

Answer 9

Involved in recuperation.
Reduced heart rate and strength of contraction.
Contraction of pupils
Increased digestive capability and saliva production.
Vasodilation of peripheral blood vessels.
Bronchi return to original diameter.

Question 10

Role of the Hypothalamus

Answer 10

Regulation of behavioural patterns/cycles.
Regulation of body temperature.
Regulation of dietary behaviour and metabolism.
Autonomic and endocrine control over internal organs,

Question 11

Anatomy of the Pituitary Gland

Division, structure, vascularisation, connection to the hypothalamus

Answer 11

Divided into anterior (adenohypophysis) and posterior (neurohypophysis).. Joins to the hypothalamus via the infundibulum. Found posterior and inferior to the optic chiasm.
Anterior: Secretes tropic hormones. Activity regulated by stimulating and inhibiting hormones from the neurosecretory cells of the hypothalamus. Vascularised by secondary plexus of hypophyseal system, connected to the primary plexus of hypophyseal system in hypothalamus by hypophyseal portal vein. Secondary plexus is emptied by the anterior hypophyseal vein.
Posterior: Connected to hypothalamus via neurons in the hypothalamic-hypophyseal tract. Vascularised by the capillary plexus of the infundibular system, which stems from the inferior hypophyseal artery.

Question 12

Hormones of the Anterior and Posterior Pituitary

Answer 12

Anterior: Human Growth hormone, thyroid stimulating hormone, ACTH, FSH, LH, PRL
Posterior: ADH, oxytocin.

Question 13

Anatomy of the Adrenal Glands

Answer 13

Three layers: Outermost capsule, cortex, innermost medulla,
Medulla contains the chromaffin cells which are neurosecretory and release epinephrine and norephinephrine upon cholinergic stimulation by the preganglionic ANS neuron.
Cortex is split into 3 zona.
Zona glomerulosa: Releases mineralocorticoids in response to angiotensin II stimulation- outermost.
Zona fasciculata: Releases glucocorticoids in response to ACTH secretion and regulates metabolism and the stress reaction-medial layer.
Zona reticularis: Negligible effect-small amounts of androgen.

Question 14

Difference between Eustress and Distress

Answer 14

Eustress: Beneficial stress response. Adaptive and only activated in the presence of a life threatening stressor. Aids in survival .
Distress: Chronic activation of the alarm response due to preception of danger. Causes the body to constantly remain in the resistance state and hence cause adverse effects.

Question 15

Mechanism of Phase 1 of the alarm response

Answer 15

The Fight or Flight response, triggered by activation of the sympathetic division of the ANS.
Immediate mobilisation of the body’s resources for survival.
Increasing rate of transport of glucose and oxygen to effectors most effective at warding off danger. Reduces availability of glucose and oxygen to non-crucial organs.
Stimulate the release of NE and E from the adrenal medulla to extend the alarm response.
Causes resistance to stress to increase immediately after stressor stimulation.

Question 16

Mechanism of Phase 2 of the alarm response

Answer 16

Extended alarm response stimulated by the release of norepinephrine and epinephrine from adrenal medulla. Sustains and enhances the alarm response by sending out hormones.
Does not add any effects to the alarm response.

Question 17

Mechanism of Phase 3 of the alarm response

Answer 17

Resistance reaction, stimulated by the release of cortical hormones, which in turn is stimulated by the release of ACTH, which is controlled by CRH.
Release of GHRH to stimulate hCG release from liver.
Stimulates TRH release to stimulate TSH release to increase thyroid activity and upregulates metabolism.
Continues to prepare the body to ward off danger after the initial FoF response.
Body mobilises resources to deal with continued stressors at the cost of long term processes.

Question 18

Interaction between the immune system/Health and ANS/endocrine system

Answer 18

IL-1 released by macrophages stimulates the release of ACTH from the hypothalamus, which causes the secretion of cortisol. Cortisol triggers the resistance reaction and downregulates the immune response-this is how excess stress can lead to disease by prolonged inhibition of immune system.
Neurons in the ANS can be connected to the secondary lymphoid organs and influences immune system responses.
Habitual hostility: Constant sympathetic activation causes organs to remain in stressed states. Leads to cardiac damage as the heart is constantly forced to contract harder.

Question 19

Mechanism of Action: Lipid-Soluble hormones

Answer 19

Diffusion past cell surface and nuclear phospholipid bilayers and binds to receptors in the nucleus.
Activated receptor-hormone receptor binds to DNA and affects gene expression.
Altered gene expression causes different mRNA to be produced, which affects ribosomal translation.
New protein produced as a result.

Question 20

Mechanism of Action: Water-Soluble hormones

Answer 20

Hormone binds to G-protein-coupled receptor and activates G-protein.
G protein activates adenylyl cyclase, which converts ATP to cAMP.
cAMP acts as a secondary messenger and activates protein kinases.
Protein kinases phosphorylates or otherwise modifies the target protein to change its function.

Question 21

Timings of the three phases of the stress response.

Answer 21

Initial alarm: Activated in milliseconds but also as quickly deactivated.
Extended: Activated in seconds and lats for minutes. Exists because the few milliseconds where the initial alarm system is activated is too short to deal with a stressor.
Resistance: Activated in minutes and lasts for hours.

Question 22

Difference between the autonomous and somatic motor systems

Answer 22

Autonomous: Output controlled by involuntary parts of the CNS (limbic system, hypothalamus, brainstem, spinal cord)
Consists of a myelinated preganglionic and unmyelinated postganglionic segment.
Cholinergic and adrenergic.
Innervates smooth muscle, glands and cardiac muscle.
Somatic: Controlled by the motor cortex.
Single myelinated neuron.
Cholinergic
Innervates skeletal muscle.