ANAT 7390 Lecture Notes - Lecture 1: Postcentral Gyrus, Unipolar Neuron, Inner Ear
17 Jun 2018
School
Department
Course
Professor
1
TOPIC IV: NERVOUS SYSTEM II - SENSORY “INPUT”
A) Afferent Nervous System
1) Interpretation of Sensory Stimuli:
- Stimuli are detected by receptors (only respond to a specific stimulus e.g. temp.)
- Receptors can be:
a) dendrites on a unipolar neuron
b) an individual cell that synapses to a neuron e.g. hair cell (internal ear)
- What happens when a receptor (R) is stimulated?
a) stimulus causes opening of gated channels (usually Na+) on receptor
membrane
b) GP on receptor membrane (stim. becomes electrical)
IF:
i) receptor = dendrite of unipolar neuron and GP (depol) directly
generates an AP = a generator potential
ii) receptor = individual cell e.g. hair cell (no axon) = a receptor
potential → nt onto associated neuron → EPSP on neuron
→ generates an AP
2) Types of Receptors
a) Phasic receptors
- receptors respond to stimulus change
- in the presence of a constant stimulus, show adaptation (usually ↓ in
sensitivity)
- e.g. 1: put a hat on → bursts of APs (feel it) → then get ↓ in AP frequency to
CNS (can’t feel it) even though stim. maintained at constant strength
- e.g. 2: take hat off – bursts of APs – feel it again
b) Tonic receptors
- frequency of APs remains constant - NO adaptation
- give continuous info e.g. posture, condition, pain ⇒ protective
- monitor presence + intensity of stimulus
3) How does brain perceive different types of stimuli?
- mainly by type of receptor stimulated
- axon activated by receptor → synaptic connections to part of CNS concerned with that
sense (hardwired from receptor to brain - always knows ‘who’ is calling (type of
receptor) and from where (location))
- e.g. 1: stimulate Meissner’s corpuscle (touch receptor) in right index finger ⇒ impulses
to postcentral gyrus region for right index finger
- e.g. 2: mechanical pressure on eyeball → “seen” as light - ALL signals received from
retina perceived as light
Document Summary
Topic iv: nervous system ii - en ory (cid:862)input(cid:863: afferent nervous system, interpretation of sensory stimuli, types of receptors, dendrites on a unipolar neuron, an individual cell that synapses to a neuron e. g. hair cell (internal ear) Stimuli are detected by receptors (only respond to a specific stimulus e. g. temp. ) In the presence of a constant stimulus, show adaptation (usually in. E. g. 1: put a hat on bursts of aps (feel it) then get in ap frequency to. E. g. 2: take hat off bursts of aps feel it again. Cns (cid:894)ca(cid:374)(cid:859)t feel it(cid:895) even though stim. maintained at constant strength: phasic receptors generates an ap = a generator potential. Frequency of aps remains constant - no adaptation. Axon activated by receptor synaptic connections to part of cns concerned with that sense (hardwired from receptor to brain - always k(cid:374)ows (cid:858)who(cid:859) is calli(cid:374)g (cid:894)type of receptor) and from where (location))
