12 October 2011Chapter 7: Sensory Physiology

Lab next week: Part 1: Visual System B (lecture/demo)Part 2: Sensory physiology experiment: Cutaneous receptor distributionPart 3: Auditory System (lecture/demo)

Special Quiz on Cranial Nerves: Name, number & function on MondayVisual System will be a separate section on Test # 2.

1QQ # 16 for 8:30 class

1. Which of the following are correct statements:a) Most sympathetic postganglionic axons release NE.b) Most parasympathetic postganglionic axons release ACh.c) the urinary bladder will relax if exposed to ACh.d) axons of parasympathetic neurons are found in thoracic and lumbar spinal nerves.e) NE and EPI can cause contraction of arterioles.

2. Which of the following are correct statements:a) Most sympathetic preganglionic axons release NE.b) Most parasympathetic postganglionic axons release ACh.c) intestinal motility and secretion will increase as parasympathetic activity increases. d) The vagus nerve provides parasympathetic innervation to the rectum and urinary bladder.e) Smooth muscles of arterioles have adrenergic and mucarinic receptors.

1QQ # 16 for 8:30 class

1. Which of the following are correct statements:a) Most sympathetic postganglionic axons release NE.b) Most parasympathetic postganglionic axons release ACh.c) the urinary bladder will relax if exposed to ACh.d) axons of parasympathetic neurons are found in thoracic and lumbar spinal nerves.e) NE and EPI can cause contraction of arterioles.

2. Which of the following are correct statements:a) Most sympathetic preganglionic axons release NE.b) Most parasympathetic postganglionic axons release ACh.c) intestinal motility and secretion will increase as parasympathetic activity increases. d) The vagus nerve provides parasympathetic innervation to the rectum and urinary bladder.e) Smooth muscles of arterioles have adrenergic and mucarinic receptors.

1QQ # 16 for 9:30 class1. Which of the following are correct statements:

a) Sympathetic preganglionic axons use NE as their neurotransmitter.b) Most parasympathetic postganglionic axons release ACh.c) the urinary bladder will contract if exposed to NE.d) Some cranial nerves have preganglionic sympathetic axons.e) Smooth muscles and glands typically have adrenergic and muscarinic receptors.

2. Which of the following are correct statements:a) Most sympathetic preganglionic axons release NE.b) Most parasympathetic postganglionic axons release ACh.c) intestinal motility and secretion will increase as parasympathetic activity increases. d) The vagus nerve provides parasympathetic innervation to the rectum and urinary bladder.e) Smooth muscles of arterioles have adrenergic and mucarinic receptors.

1QQ # 16 for 9:30 class1. Which of the following are correct statements:

a) Sympathetic preganglionic axons use NE as their neurotransmitter.b) Most parasympathetic postganglionic axons release ACh.c) the urinary bladder will contract if exposed to NE.d) Some cranial nerves have preganglionic sympathetic axons.e) Smooth muscles and glands typically have adrenergic and muscarinic receptors.

2. Which of the following are correct statements:a) Most sympathetic preganglionic axons release NE.b) Most parasympathetic postganglionic axons release ACh.c) intestinal motility and secretion will increase as parasympathetic activity increases. d) The vagus nerve provides parasympathetic innervation to the rectum and urinary bladder.e) Smooth muscles of arterioles have adrenergic and mucarinic receptors.

Sensing the world • Sensory coding: sensory systems code for modality, intensity, location, and duration of external stimuli.

• Transduction: the conversion of a physical stimulus into a change in membrane potential (electrochemical signal) – Signals are transmitted in the form of

graded potentials, action potentials, and synaptic interaction

• Receptors: cells or regions of cells that respond to specific stimuli and perform transduction– The process of sensory coding starts

here– Specificity: receptors are often

sensitive to specific stimuli; varies with receptor type

S 1

Changes of membrane potential depend on ion channels

Reminder: leak channels are not gated.

S 2

Receptors for gustation

Receptor proteins

Receptor cell

1st order sensory neuron

S 3

5 different types of receptor proteins (but not all in the same cell)

Hair cells = specialized receptor cell with

mechanically-gated K+ channels.

Receptors for audition (hearing)and

equilibrium(movement and orientation to gravity)

Receptor cell

1st order sensory neuron

S 4

Scanning electron micrograph of hair cells from the bullfrog inner ear, which contain the mechanically-gated ion channel TRPA1. (Image courtesy of Howard Hughes Medical Institute)

Mechanically gated K+ channels in stereocilia of hair cells

S 5

Receptor cells withreceptor proteins.

Encapsulated

S 6

TZ

TZTZ

Somatosensory and the sensation of touch

Skin is largest sense organ: up to 2 million receptors

Sensory system must code for where (location), how hard (intensity), how long (duration), and modality (sense of touch, temperature, vibration, wet/dry, damage (pain; noxious)).

S 7

Somatosensory: sensation of touch, vibration, pain, and temperature

Deep

Superficial

Sustained stimulus

Fluctuating stimulus Encapsulated nerve endings

S 8

“Adequate” stimulus: the stimulus type to which areceptor responds best (lowest threshold.)

This diagram is misleading: Different types of receptors are NOTpart of the same sensory neuron!

S 9

Labeled Lines:Different sensory modalities are transmitted separately along distinct pathways.

S 10

Figure 7.15Stimulus Localization& Modality & Intensity

Three neurons to the cortex!

Labeled Line

S 11

Anterolateral (spinothalamic) tract1st order synapses onto 2nd order in spinal cord, 2nd order axon decussates in spinal cord, travels to thalamus in contralateral anterolateral tract, synpases onto 3rd order neuron in thalamus, which sends its axon to SSC.

Dorsal column-medial lemniscal tract1st order axons ascend in ipsilateral dorsal columns to synapses onto 2nd order in dorsal column nuclei of brainstem, 2nd order axon decussates in brainstem, travel to thalamus to synpases onto 3rd order neuron, which sends it axons to SSC.

Right side

Right sideRight side

Right side

Proprioception

S 12

Regions more densely innervated by sensory receptors occupy more cortical tissue.

Somatotopy in the Somoatosensory Cortext (post-central gyrus.)S 13

Referred pain

Who cares?

S 14

S 16

Referred PainFig 7-18 p. 200 of text

Receptive field = the area of the body that, when stimulated, leads to activity in a neuron.

= 1st order sensory neuron

Could be encapsulated

S 17

Dorsal column-medial lemniscal tract1st order axons ascend in ipsilateral dorsal columns to synapses onto 2nd order in dorsal column nuclei of brainstem, 2nd order axon decussates in brainstem, travel to thalamus to synpases onto 3rd order neuron, which sends it axons to SSC.

Right side

Right sideRight side

Right side

Proprioception

Receptive field = the area of the bodythat, when stimulated, leads to activity in a neuron.

1st, 2nd, and 3rd order sensory neurons each have receptive fields.

S 18

Receptor potentials

• Graded potentials are the result of transduction within a receptor. Transduction produces a receptor potential

• Amplitude is usually in proportion to the stimulus intensity

• Specialty receptor cells with no axon (visual, gustatory, auditory, and vestibular systems). The graded receptor potentials will directly change amount of NT secretion onto 1st order sensory neuron.

• Receptors with axons (somatosensory and olfactory systems) have a trigger zone and receptor potentials generate action potentials

e.g. somatosensory

e.g. gustatory

S 19

Activation of mechanically gated channels

Receptors and transduction

Could be encapsulated

S 20

Sensations to touchMechanoreceptors contain receptor proteins that respond to

stretching, distortion, or pressure on the peripheral plasma membrane

S 21