L21

Question 1

explain the autonomic nervous system + its 2 divisions

Answer 1

• Controls
  ○ Blood pressure
  ○ Heart/breathing rate
  ○ Body temp.
  ○ Digestion
  ○ Metabolism
  
  • Has 2 divisions, are usually antagonistic to each other
    ○ Sympathetic
    § Fight or flight
    § leads to increased alertness + metabolism for a emergency○ Parasympathetic
    § Rest + digest
    slows down most body activities

Question 2

explain the somatic nervous system

Answer 2

○ Sensory (touch, pain, temp., sight) + motor neurons (skeletal muscle)
○ Conscious perception + voluntary control
○ Has 1 motor neuron
○ The myelinated axon of a single somatic motor neurons extends from the central nervous system to the skeletal muscle fibre it innervates (using Ach, receptor = nicotinic/ligand fated ion channel)

Question 3

Motor neurons involved in the the autonomic nervous system

Answer 3

○ Has 2 motor neurons in series
○ 1st preganglionic neuron has its cell body in the CNS
○ Axon extends to an autonomic ganglion
2nd neuron has its unmyelinated axon extending from the ganglion to the effector (smooth/cardiac muscle + glands)

Question 4

//steps of the sympathetic autonomic motor pathway

Answer 4

1. Goes from spinal cord- preganglionic neuron
   
   2. Preganglionic fibre
   3. Sympathetic ganglion (ach at nicotinic receptors)
      ○ Vertebral chain ganglia
      ○ Pre-vertebral chain ganglia
   4. Postganglionic fibre
2. Goes to NA adrenergic receptors of effector (e.g. Glands, heart, urinary bladder)

Question 5

explain the sympathetic nervous system

Answer 5

• Preganglionic neurons send out fibres in the 12 thoracic + first 2/3 lumbar segments
  
  • Preganglionic fibres are short with postganglionic being longer
    Can accelerate heart rate, constrict blood vessels, pupil dilation, activate goose bumps

Question 6

//steps of the parasympathetic autonomic motor pathway

Answer 6

1. Goes from spinal cord- preganglionic neuron
   
   2. Preganglionic fibre
   3. parasympathetic ganglion (ach at nicotinic receptors)
   4. Postganglionic fibre
2. Goes to Ach at muscarinic receptors of effector (e.g. Glands, heart, urinary bladder)

Question 7

explain the parasympathetic nervous system

Answer 7

• Cell bodies of the preganglionic neurons send out fibres at the brainstem + the sacral segments of 2-4 of the spinal cord
  
  • Preganglionic fibres longer, with postganglionic being shorter (often inside the target organ)
    Stimulates production of saliva, making tears

Question 8

explain ANS neurotransmitters + receptors

Answer 8

• Based on the neurotransmitter they produce + release, so are either cholinergic or adrenergic
  
  • Cholinergic- releases Ach, binds to either nicotinic or muscarinic receptors
    Adrenergic neurons release noradrenaline, which binds onto adrenergic receptors (alpha and/or beta)

Question 9

explain pre-ganglionic neurons

Answer 9

○ Ach
○ Nicotinic receptors
Shorter in sympathetic, longer in parasympathetic

Question 10

explain post-ganglionic neurons

Answer 10

○ Parasympathetic
§ Ach
§ Muscarinic receptors
○ Sympathetic
§ Noradrenaline
§ Alpha + beta receptors
Longer in sympathetic, shorter in parasympathetic

Question 11

explain the 2 alpha receptors

Answer 11

• Alpha 1 receptors- vasoconstriction + increased liver glucose production
  Alpha 2 receptors- decreased insulin, vasodilation,, inhibitory responses for GI

Question 12

explain the 3 beta receptors

Answer 12

• Beta 1 receptors- increased heart rate, increased heart contractility, increased renin release
  
  • B2 receptors- increased lipolysis (fat breakdown), increased liver glucose production, smooth muscle relaxation, bronchodilation
    B3 receptors- increased lipolysis, increased glycogen breakdown

Question 13

explain the effects of muscarinic receptors

Answer 13

• Increased insulin/glucagon secretion
  
  • Increased GI activity
  • Erection
  • Vasodilation
  • Decreased heart rate
    Decreased contractility

Question 14

explain the nervous system and homeostasis

Answer 14

• Involved in maintaining homeostasis
  reflex arc
  Main integration centre for ANS reflexes is the hypothalamus

Question 15

//explain the regulation of the autonomic nervous system

Answer 15

• Cerebral cortex (frontal lobe)
  
  • Limbic lobe (emotional input)
  • Hypothalamus (‘boss’ of system)
  • Reticular formation of brain stem (regulation of pupil size, respiration, heart, blood pressure)
    Spinal cord (urination, defecation, erection)

Question 16

What region regulates heart + blood vessels

Answer 16

• CV centre in medulla is the main region for the nervous system regulation of the heart + blood vessels