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Anat and Phys > Special senses > Flashcards

Special senses Flashcards

1
Q

General senses

A

Receptors are scattered through the body. E.g touch, pressure, pain, vibration, tem

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2
Q

Special senses

A

have a special organ/structure with distance receptor cells devoted to it and all localised in the head region

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3
Q

Importance of sensory systems

A

The ability to sense changed in the environment and in the body allowing survival
Survival depends on:
- Sensation: the awareness of changed in the internal and external environment
- Perception: the conscious interpretation of those stimuli
How we interpret sensation determines how:
- we develop physically, cognitively
- our memories are formed
- we interact socially
- we become unique

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4
Q

Simple organisms e.g Hydra

A
  • Respond to light, pH and nutrient presence
  • basic nerve connections and primitive histology
  • hydra defy standard sensory receptor modelling
  • Show endogenous activity when kept in a homogenous environment
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5
Q

General principles in higher animals
Receptor cells
Purpose

A
  • specialised receptor cells are distributed throughout eukaryotic organisms
  • purpose: to convert physical or chemical signal into electrical signal so that is can be used as an action potential
  • electrical signals travel PNS to CNS
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6
Q

Afferent

A

Signals received and processed by CNS

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7
Q

Efferent

A

Signals from CNS elicit appropriate response in body

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8
Q

Free nerve endings

A

Non-encapsulated
Pain and thermoreceptors
Light tough and hair follicle e receptors

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9
Q

Encapsulated nerve endings

A

Pacinian (lamellar) corpuscles for touch and pressure
Tactile corpuscles for discriminative touch
Muscle spindles: proprioceptors respond to muscle stretch

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10
Q

Specialised receptor cells e.g.

A

Photoreceptor cells in the retina of the eye respond to light stimuli - rods
Tastebuds

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11
Q

Sensory receptors process

A

Stimuli in the environment activate specialised receptor cells in the PNS –> integration in brain –> send motor output to effectors
Different types of stimuli are sensed by different types of receptor cells

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12
Q

How are receptor cells classified

A

Structurally by cells type, position and function

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13
Q

General arrangement of neurones in ascending tracts: first order neuron

A

Has the receptor
Synapses to second order neutron
In grey matter of spinal cord or in medulla oblongata

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14
Q

General arrangement of neurones in ascending tracts: second order neuron

A

interneuron
crosses over to other side
Decussation
Ascends to thalamus

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15
Q

General arrangement of neurones in ascending tracts: this order neuron

A

Axons pass to somatosensory cortex

There the sensory information is received and interpreted = perception of peripheral stimulus

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16
Q

Ascending tracts

A

Afferent signals travel towards brain for processing

17
Q

Descending tracts

A

efferent signals from CNS to elicit appropriate response elsewhere in body

18
Q

Spinal cord

A
  • Ascending and descending tracts located in specific areas of the spinal cord
    Allocated pathways for different senses so that the brain knows where the stimuli is coming from
    Different nerve tracts lead to different parts of the brain
    Tracts are symmetrical
19
Q 
Ascending pathways
Dorsal 
Tracts
Conscious 
Sub-conscious
A

Somatosensory signals travel along three main pathways on each side of spinal cord:
Dorsal column pathway: Spinothalamic tract and spinocerebellar tract
Conscious information: dorsal column,ns, fasciculus gracilis, fasciculus cuneatus, spinothalamic tracts
Subconscious: spinocerebellar

20
Q

Descending Pathways

A

Descend from brain to effector region - motor neurone to create effect
In the pyramidal pathways of the spine

21
Q

Sensory receptors (2)

A

Stimuli in the environment activate specialised receptor cells in the PNS –> integration in brain –> send motor output to effects
Different types of stimuli are sensed by different types of receptor cells
Receptor cells classified structurally by cell type, position and function

22
Q

Exteroceptors

A

Respond to stimuli arising outside of body
Receptors in skin for touch, pressure, pain and temperature
Most special sense organ

23
Q

Interceptors (visceroceptors)

A

Respond to stimuli arising in internal viscera and blood vesseld
Sensitive to chemical changes, tissue stretch, and temp changes

24
Q

Proprioceptors

A

Respond to stretch in skeletal muscles, joints, ligaments, and connective tissue covering of bones and muscles
Inform brain of one’s movements

25
Q

Mechanoreceptors

A

Stretching of cell membrane opens ion channels
Respond to physical stimuli like touch, pressure, vibration and stretch. Balance, sounds, muscle length and tension, joint position and movement

26
Q

Thermoreceptors

A

Allows ions to enter cell, eliciting generator potential
Several proteins that detect temperature
Sensitive to changes above or below normal body temp
Free nerve endings, mainly in skin, lining oral cavity and on tongue

27
Q

Chemoreceptors

A

Chemicals bind to specific receptors on cell membrane

Respond to chemicals (smell, taste, blood chemistry) = external (nose) or internal

28
Q

Photoreceptors

A

Initiate chain of reactions to cause breakdown of 2nd messenger molecule and closure of ion channels
Always has an influx of ions to get the membrane potential
Respond to light energy

29
Q

Osmoreceptors

A

Respond to solute concentrations of body fluids

30
Q

Nociceptors

A

Free nerve ending chemoreceptors that respond to tissue-damaging stimuli
In the brain the signals are perceived as pain
Sensitive to pain-causing stimuli (extreme heat or cold, excessive pressure, inflammatory chemicals) - have different properties in terms of where

31
Q

Neuronal communication after detection

A

For sensation to occur, the stimulus must excite a receptor and the action potential must be created
This action potential must reach the CNS.
The transmission of a nerve impulse across a synapse is by means of a chemical called a neurotransmitter

32
Q

Neurons characteristics

A

Long-lived (>100)
Hugh metabolic rate - depends on continuous supply of oxygen and glucose
Plasma functions in electrical signalling and cell-to-cell interaction during development

33
Q

Chemical synapses

A
  • Neuron secrete neurotransmitter that binds to specific receptors in cell membrane of second neuron
  • most common way in which neurones communicate
  • axon terminal contains packets of neurotransmitter e.g. acetylcholine
  • electrical signal to chemical signal and then back to an electrical signal when it reached the next neuron
34
Q

Signal transmission at synapse

A
  1. AP arrive at axon terminal
  2. Voltage-gated Ca2+ channels open
  3. Ca2+ enters cell – communicates with the synaptic vesicles to begin the transfer
  4. Ca2+ signals to vesicles
  5. Vesicles move to membrane
  6. Vesicles dock and release neurotransmitter by exocytosis
  7. Neurotransmitter diffuses across synaptic cleft and binds to specific receptors
  8. Binding of neurotransmitter to receptor activated signal transduction pathway
35
Q

Sensory transduction

A

Physical energy –> electrical energy
electrical energy produced by receptor = receptor potential
Stimulus acts by affecting opening/closing of channels or affects calcium levels inside separate cell

36
Q

Graded potentials and special senses

A
  • a receptor potential is a graded response to a stimulus that may be depolarising or hyperpolarising
  • receptor potentials have a threshold in stimulus amplitude that must be reached before a response is generated
  • graded means the amplitude of the receptor is proportional to the size of the stimulus
  • the transduction process couple’s stimulus detection to the opening or closing of ion channels
37
Q

Stimulus intensity: frequency or recruitment

A
  • the more intense stimuli produce higher frequency of action potentials
  • stimuli of increasing intensity activate, or recruit, greater number of receptors
38
Q

What happens in the brain

A
  • any given neurone usually received signals from many other neurons
  • special sense pathways can form complex neural pathways when they enter the brain
  • when groups of neurones synapse there can always be integration

Anat and Phys (19 decks)

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