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Human Physiology 1 > Lecture 16 Outline > Flashcards

Lecture 16 Outline Flashcards

1
Q

Smooth muscle, cardiac muscle, glands & the effector organs (made up of muscle & gland tissue) as well as the visceral stimuli are…

A

unconscious

  • may or may not be aware of this (unconscious)
  • it’s detected & sent back to the CNS & ultimately processed again (ex: not aware of min to min blood pressure, heart rate ex)

key role in homeostasis

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2
Q

Describe the Autonomic Nervous System (ANS)

A

Innervates organs whose functions are not usually under voluntary control

Reflexes are important for autonomic control

For homeostatic control, effectors are often visceral organs and blood vessels
- changing diameter of blood vessels through the action of smooth muscle - dilating or constricting smooth muscle

Autonomic means self-governed

Most visceral effectors do not need the ANS to function, only to adjust their activity to match the body’s needs to maintain homeostasis
– Heart rate for example.

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3
Q

Why are reflexes important for automonic control?

A

– Sensory info may be processed within hypothalamus, limbic system, or even at the level of spinal cord

– Reflex (stimulus) may evoke CHANGES in autonomic output,
• in order to RETURN to a SETPOINT (negative feedback - homeostasis usually)
• In order to “FIGHT or FLIGHT” (feedforward - intended to prevent change in setpoint)

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4
Q

Why do we need sensory info?

A

need sensory info with regard to what’s happening inside your body in order to make decisions about autonomic control

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5
Q

What does autonomic means self-governed imply? And what are examples of “conscious control”?

A

its actions usually INvoluntary (without conscious intent or awareness - happen by itself)

there are examples of “conscious control)

  • micturation (to pee or not to pee)
  • control of heart rate (with practice), biathlon for ex
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6
Q

Most visceral effectors do not need the ANS to function…

A

only to adjust their activity to match the body’s needs to maintain homeostasis
– Heart rate for example.
*beats by itself, does not need the ANS to beat (you can remove all autonomic input - sympathetic/parasympathetic from the heart & it will continue to beat just fine
- issue is the ANS allows your heart to speed up or slow down

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7
Q

Describe the ANS anatomy

A

general autonomic nerve pathway output

  • extends from CNS to an innervated organ
  • 2-neuron chain
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8
Q

What is the 2-neuron chain? List and describe

A
  • Preganglionic fiber (synapses with cell body of second neuron)
  • will excite postganglionic fiber b/c the synapses happen in the autonomic ganglion
  • Postganglionic fiber (innvervates effector organ or tissue)
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9
Q

What is a ganglion?

A

mass or group of neuronal cell bodies knot-like mass of tissue

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10
Q

Describe the synaptic terminals in the ANS

A
  • no signal terminal
  • end of synaptic region is a series of varicosities on the axon
  • specialized in exactly the same way you would call a typical synaptic terminal (secretion of n.t., but it’s not the terminal end of the axons)
  1. contact
  2. axon meanders over that surface of the tissue but at regular intervals we’ll see these bulges called varicosities
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11
Q

What is the key difference b/t what we see in the CNS & what we see from the action from the postganglionic neurons on their targets?

A

Varicositities - specialized for releasing n.t. from that postganglionic neuron

*the synapse & synaptic connections are seen as these varicosities or chain like connections from that postsynaptic tissue

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12
Q

Varicosities

A

specialized for releasing n.t. from that postganglionic neuron

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13
Q

What is the Sympathetic Chain Ganglia?

A
  • ganglia (enlargements) that run parallel to the spinal cord
  • a lot of the sympathetic NS uses these paravertebral ganglion
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14
Q

Describe the SYMPAthetic Nervous System

A

T1-L2 (1st thoracic to the 2nd lumbar)

Cell bodies & axons of PREganglionics originate in THORACIC & LUMBAR regions of spinal cord

  • will send out axons & those axons or the preganglionics will make a synapse somewhere on the cell bodies of the post ganglionics & then from there, the postganglionics will make a synapse on the target organ
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15
Q

What are the defining characteristics of the SYMPAthetic Nervous System

A

Most PREganglionic fibers are SHORT

LONG POSTganglionic fibers

therefore not a long axon of this preganglionic, but the axon of the postganglionic is really quite long going from chain ganglionic all the way to the heart

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16
Q

For the SYMPAthetic Nervous System, the axons do 1 of 3 things after exit spinal cord:

A
  1. Make a synapse in a SYMPATHETIC CHAIN GANGLION
  2. Pass thru SCG & synapse in the Adrenal Medulla
  3. Pass thru SCG & synapse in a collateral ganglion
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17
Q

PREganglionic fibers (of the SYMPATHETIC) release _____ ALWAYS

A

ACh

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18
Q

MOST POSTganglionic fibers (of the SYMPAthetic) release…

A

NE

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19
Q

The adrenal medulla is a…

A

modified sympathetic ganglion

  • truly & dev. neurons?
  • true part of the sympathetic NS b/c developmentally the adrenal medulla cells really are modified neurons (grew up/born as neurons)
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20
Q

Describe the path of the SYMPAthetic NS with the adrenal medulla

A
  1. Spinal cord innovated by a PREganglionic sympathetic neuron
  2. Adrenal medulla (modified neurons - born as neurons) release ACh onto those neurons
    - the chromaffin cell is a modified postganglionic sympathetic neuron
  3. When stimulated they’ll release Epinephrine (primarily) is a neurohormone that enters the blood
  4. To target tissues
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21
Q

Describe the PARAsympathetic Nervous System

A

fibers originate from CRANIAL & SACRAL areas of CNS
- many of the cell bodies of those neurons will either be found as 1 of the cranial nerves OR they’re far away in the sacral region of the spinal cord

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22
Q

What are the defining characteristics of the PARAsympathetic nervous system?

A

PREganglionic fibers are LONGER

VERY SHORT POSTganglionic fibers (hard to find sometimes (ex: on heart)

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23
Q

PREganglionic fibers (of the PARAsympathetic NS) release…

A

ACh

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24
Q

POSTganglionic fibers (of the PARAsympathetic NS) release…

A

ACh

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25
Q

What is a similarity within the PARAsympathetic NS compared to the SYMPAthetic NS in terms of what they release?

A

the PARA uses ACh for BOTH synapses in contrast to that the SYMPA uses ACh b/t the pre & post but usually uses neuroepinephrine at the post ganglionic

26
Q

What is true for SYMP/PARAsympathic in terms of convergence & divergence in ANS?

A

each POSTganglionic neuron receives synapses from many PREganglionics (=convergence)

27
Q

What is convergence & divergence like in the SNS?

A

Each preganglionic neuron branches many times to synapse on many different postganglionic neurons (= divergence).
Ratio of pre:post neurons is 1:10 -1:30 (more post)

28
Q

What is convergence & divergence like in the PNS?

A

Each preganglionic neuron branches to synapse on postganglionic neurons (= divergence).
Ratio of pre:post neurons is 1:4 (lower than SNS)

  • can activate selective branches more easily
29
Q

MORE DIVERgence in…

A

SNS

30
Q

MASS ACTION in…

A

SNS

- SNS tends to respond as a unit

31
Q

What are cranial nerves?

A

series of nerves found emanating mostly FROM the BRAINSTEM, not all but many eminate from the brainstem, a SERIES OF 12
- can either be output axons; so the nerve is a bundle of axons

32
Q

Output axons

A

control things like MOVEMENT of MUSCLE in the EYE, can be SENSORY: can receive from the eye or olfactory for ex, or they are mixed so the nerves contain axons that carry info away from the CNS to the target organs or it carries info back into the CNS (so sensory info)

33
Q

List & describe 4 of the cranial nerves have PARAsympatethic function

A

– OCULOMOTOR NERVE: control the lens and pupil of the eye.
– FACIAL NERVE: tear glands, salivary glands, nasal glands
– GLOSSOPHARYNGEAL NERVE: salivary glands
*– VAGUS NERVE: 70-90% of all parasympathetic fibres. Innervates the viscera.

34
Q

What is the vagus nerve?

A

70-90% of all PARAsympathetic fibres. Innervates the viscera (organs)

35
Q

Describe the Vagus Nerve (tenth CN)

A

someone who wonders (wonders through visera)

  • 10th cranial nerve
  • “wandering”
  • many branches
    • innervates ALL organs except adrenal medulla & some parts of the colon
36
Q

The vagus nerve is part of a…

A

reflex arc

37
Q

Describe the Vagus nerve pathway

A
  1. Vagus nerve (mixed nerve) CARRIES SENSORY INFO FROM most of the VISCERA
    - many of these sensory afferents project topographically to Nucleus of the Solitary Tract (NST or NTS) in the brainstem
  2. The sensory info is PROCESSED WITHIN the NTS.
    - The NTS may also project axons to “higher” parts of the brain, hypothalamus and cortex
  3. Vagus nerve CARRIES EFFERENT (parasympathetic) information TO REGULATE/MODULATE ORGAN FUNCTION
    - both efferent (are preganglionic of the parasymp & afferent info)
38
Q

Sympathetic recap

A

short pre
long post

usually NE release from post

occasionally ACh

39
Q

Parasympathetic recap

A

long pre
short post

also nicotinic receptors occasonally…

40
Q

Which autonomic branch tends to have a longer lasting effect on target organs?

A

The SNS tends to have a longer lasting effect than PNS (on target organs).

41
Q

The SNS tends to have a longer lasting effect than PNS (on target organs). Why?

A
  1. ACh QUICKLY broken down by acetylcholinesterase
  2. NE more persistent than Ach, because breakdown mechanisms are slower for NE than for ACh
    • NE Transported back into the neuron (reused & recycled quickly)
    • NE Degraded by
    – catechol-O-methyl transferase (COMT)
    – Monoamine oxidase (MAO)
    *these 2 enzymes are not as efficient as acetylcholinesterase
    • NE Picked up by blood (no DEGRADATIVE enzymes present in blood)
42
Q

Describe the SNS (nor epi) receptors on target organs for the ANS

A 
SNS (nor epi)
– α1 (phospholipase c)
– α2 (DEcrease cAMP)
– β1 (INcrease cAMP)
– β2 (BOTH INcrease and DEcrease cAMP)*
– β3 (INcrease cAMP)

Think: Pdibi

43
Q

Describe the PNS (ACh) receptors on target organs for the ANS

A 
PNS (ACh)
– Nicotinic AChR (ligand gated ion channel)
– Muscarinic AChR (GPCR) 
• M1 (phospholipase c)
• M2 (decrease cAMP)
• M3 (phospholipase c)
44
Q

SNS activates the ______ ______ to release ______ amounts of epinephrine (some norepi)

A

adrenal medulla

LARGE

45
Q

Remember that 2nd messenger signaling often affects…

A

ion channels

46
Q

Hard to predict effect of SNS vs PNS activation. Helps to relate back to:

A

fight or flight - strenuous activity, threats

rest & digest - housekeeping, relaxing

47
Q

What are the effects of ANS on the HEART?

A

SYMPA NS

  • INCREASED rate, INCREASED force of contraction (of whole heart)
  • activated when stressed
  • purpose of those are to increase the circulation of blood & to defect skeletal muscle blood for ex

PARA NS
- DECREASED rate, DECREASED force of contraction

48
Q

What are the effects of ANS on the EYE?

A

SYMPA NS

  • DILATION of pupil
    • not significant for refocusing lens

PARA NS

  • CONSTRICTION of pupil
  • (plays key role for) adjustment of eye for near vision
49
Q

What are the effects of ANS on the EXOCRINE PANCREAS?

A

SYMPA NS
- INHIBITION of pancreatic exocrine secretion

PARA NS
- STIMULATION of pancreatic exocrine secretion (imp. for digestion)

50
Q

What are the effects of ANS on the SALIVARY GLANDS?

A

SYMPA NS
- stimulation of SMALL VOLUME of THICK saliva rich in MUCUS (mouth gets dry if nervous)

PARA NS
- stimulation of LARGE VOLUME of WATERY saliva rich in ENZYMES (useful for digestion)

51
Q

Exocrine pancreas

A

production of enzymes such as trypsin, pancreatic lipase, & pancreatic amylase

52
Q

Homeostasis is a dynamic balance b/t…

A

the autonomic branches (balance of para & sympa)

  • rest & digest: para activity dominates
  • fight or flight: sympa activity dominates

*usually some activity of both of them simultaneously but it’s all about the balance

53
Q

Describe Dual Innervation

A

most of your organs have dual innervation
- input from both SNS interval & PNS

NOT always balanced
- digestive has much more PNS than SNS

54
Q

Dual innervation effect can be…

A

antagonistic or complimentary

55
Q

Antagonistic Dual Innervation

A

– The heart is innervated by BOTH
• SNS increases heart rate and force of contraction
• PNS decreases heart rate and force of contraction

– The iris innervated by BOTH
• SNS innervates the pupillary dilator
• PNS innervates the pupillary constrictor

56
Q

Complimentary Dual Innervation

A

– Activation of SNS and PNS produce similar results
• Salivary glands are innervated by both SNS and PNS
– Both increase saliva production, but different kinds of saliva » SNS stimulates mucus production
» PNS stimulates watery, enzyme rich saliva
• Male sexual response PNS responsible for erection, SNS responsible for ejaculation* (point and shoot)

57
Q

Describe control WITHOUT dual innervation

A

adrenal medulla, sweat glands, smooth muscle of most blood vessels receive ONLY SYMPAthetic innervation
- NOT an ex of balance of BOTH branches

58
Q

List the CNS centres contributing to autonomic regulation (PNS & SNS)

A
  • The Limbic System
  • Hypothalamus
  • Brain Stem
  • Spinal Cord
59
Q

The Limbic system

A

Integration of sensory and emotional responses with autonomic output

60
Q

Hypothalamus

A

– The major control center for autonomic output

– Hunger, thirst, thermoregulation, emotions, and sexuality

61
Q

Brain stem

A

– Gives rise to nuclei of cranial nerves that mediate several autonomic responses

62
Q

Spinal cord

A

Autonomic responses as the defecation and micturation reflexes are integrated in the spinal cord

Human Physiology 1 (32 decks)

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