Lecture 5- Structure of the PNS

Question 1

What is the PNS divided into?

Answer 1

Afferent (receptors, sense organs)

Efferent -autonomic, somatic

Question 2

What is a receptor?

Answer 2

cell allowing the body to get information about the outside/inside conditions

Question 3

What types of photoreceptors are there?
1
2
3
4
5
6
7

Answer 3

1 photo
2 mechano
3 thermo
4 osmo
5 chemo 
6 pain = nociceptors
7 electro

Question 4

What is receptor potential?

Answer 4

When receptor stimulated (thermo by temp etc) it changes the permeability to a selective ion-
-the local depolarising change in potential in case of a separate receptor cell

Question 5

What is the generator potential?

Answer 5

as receptor potential but when the receptor is a specialised afferent neuron

Question 6

What type of potential is involved in the receptors?

Answer 6

graded potential= the stronger the stimulation the greater the permeability and the larger the receptor potential. If receptor potential large enough= action potential can be triggered in the afferent neuron

Question 7

What are the two main physiological types of receptors and how does action potential flow in those?

Answer 7

-specialised afferent neuron-
local current flows between the activated receptor and the trigger zone
-cell closely associated with the afferent neuron
=such as retina= the receptor potential triggers the release of a neurotransmitter

Question 8

What is a tonic receptor?

Answer 8

• don’t adapt or very slowly, when maintained info about stimulus is needed
• stop when stimulus stops

Question 9

What is a phasic receptor?

Answer 9

-adapts rapidly
-more receptive to changes
-receptor potential rises quickly and stops quickly
(clothes wearing wouldn’t want to know all the time)

Question 10

How does the size a receptive field affect acuity?

Answer 10

The smaller the receptive field= the greater the acuity= like on your fingertips.= higher density of receptors

Question 11

How does the size of receptive fields differ in the body?

Answer 11

Greatly, fingertips, palms, teeth, muzzle= really sensitive

back= can’t even tell if one or two fingers very easily

Question 12

What is lateral inhibition?

Answer 12

• enhances contrast
• the most stimulated port enhanced stimulation and the immediate areas inhibited
• helps telling where the stimulus is
• occurs in the CNS

Question 13

Name the layers through which light must go to get to the back of the eye.

Answer 13

-cornea
-aqueous humour
-iris
-lens
-vitreous humour
-retina= rods and cones
then optic nerve

Question 14

What is the cornea for?

Answer 14

refracts the entering light

-living but no blood supply

Question 15

What is the aqueous humour for?

Answer 15

to keep the cornea inflated

Question 16

What is the iris for?

Answer 16

• it’s controlled by autonomic muscles

- contract/relax= determines how much light passes through and focuses the light onto the retina

Question 17

What is the lens for?

Answer 17

• semi solid
• can focus light
• muscles are attached to it= change its length
• only humans and small mammals have it
• • cattle and horses don’t! needed for detail!

Question 18

What is the vitreous humour for?

Answer 18

transfers light through to the retina

Question 19

How many types of retinal cells do we have/other animals?

Answer 19

• we have 3

- most animals 2 = that’s why they can’t tell red

Question 20

What is a binocular field of view and which animals have it?

Answer 20

• cats and dogs
• good for depth perception
• seeing to the front

Question 21

What is monocular field of view and which animals have it and what are it advantages?

Answer 21

• to the sides and extended behind
• blind spot directly at front
• herbivores (cattle, horses)
• so they can see approaching predators when eating grass

Question 22

What is opsin?

Answer 22

A protein in retinal cells

-detects change in light = if light is not hitting it= sends electrical signal= so light decreases the potential

Question 23

What is the structure of the ear?

Answer 23

-pinnae
-middle ear (eardrum, ossicles, Eustachian tube)
(also gutteral pouch in horses)
-cochlea (hair cells)

Question 24

What is sound?

Answer 24

Change in air pressure

Question 25

How can we hear?

Answer 25

The change in air pressure causes mechanical movement of the hairs in the cochlea which opens up ion channels- if enough stimulation = AP

Question 26

What is the vestibular apparatus for?

Answer 26

Balance and co-ordination of head and eye movements.

Question 27

What are semi-circular canals and what do they do?

Answer 27

-part of the vestibular apparatus, hairs
-detect head movements, rotation, acceleration etc.
-

Question 28

What are the Otolith organs?

Answer 28

• part of the vestibular apparatus
• tell gravitational info
• hair hang down because of gravity = that’s how you tell where is up

Question 29

What is proprioception?

Answer 29

• know where my legs are

- awareness of one’s body in space

Question 30

What is cutaneous output?

Answer 30

Pressure on my feet on the ground

Question 31

What part of the brain processes the stimuli relating to balance?

Answer 31

Cerebellum

Question 32

What are the four main taste buds?

Answer 32

1. salt
2. sour
3. sweet
4. umami

Question 33

What is the olfactory mucosa?

Answer 33

• in smelling
• has special receptor cells responsive to particular chemicals (often the ones released by individuals of other species)

Question 34

What is the vomeronasal organ?

Answer 34

• in vertebrates’ nose
• “sexual nose”
• detects pheromones in animals

Question 35

What is the Flehmen response?

Answer 35

-in horses, horses laugh, curl their lips and cover nostrils, breaths in deeply carrying pheromones into the vomeronasal organ and can determine if mare is sexually receptive

Question 36

What are mechanoreceptors for?

Answer 36

Touch + pressure

Question 37

How are mechanically-gated dendrites activated?

Answer 37

Mechanically, when moves= AP

Question 38

What are Pacinian corpuscles for?

Answer 38

Detecting deep pressure. reflect the magnitude of the stimulus.

Question 39

What are the two thermoreceptors involved in cold environment?

Answer 39

• CMR1= 28C -thermoregulatory (important for informatory role)
• AKTM1= less than 8 C (pain)
• ion gates, changing due to temperature

Question 40

What are the three thermoreceptors involved in warm environment?

Answer 40

TRPV 3- 33 C = thermoregulatory
TRPV 1- 42 C= pain/spicy (not in birds the spicy)
-also triggered by chemicals, capsicain= spicy
TRPV 2- 52 C = pain!

Question 41

What are the receptors snakes have and we don’t?

Answer 41

infrared

Question 42

What are the three types of nociceptors?

Answer 42

1. Mechanical
2. Thermal
3. Polymodal (respond to chemical from damaged tissues)

Question 43

What chemical changes the sensitivity of nociceptors?

Answer 43

• prostaglandins

- chemically enhances the pain

Question 44

How does myelination affect the speed of how fast the pain signal gets to the brain?

Answer 44

• myelinated fibres= fast = acute pain

- unmyelinated fibres = slow = chronic pain

Question 45

What is substance P?

Answer 45

• neurotransmitter involved in pain detection

- activates pathways for higher processing

Question 46

What bits are involved in the pain pathway?

Answer 46

• first have the stimulus
• then AP goes on the afferent nerve fibre to the spinal column where substance P is released
• then brainstem’s reticular formation= raises awareness
• thalamus relay station
• then cortical somatosensory areas
• also hypothalamus is involved= emotional and behavioural response to the stimuli

Question 47

What is the analgesic pathway?

Answer 47

• supresses pain transmission in the brain stem
• periaqueductal grey matter
• triggers interneurons in the dorsal root of spinal column to produce endogenous opiates (morphine like substances)
• block the pathway from proceeding further