Reflexes & General Senses Study Guide

What is a reflex?

An involuntary and instantaneous response to a stimulus.

reflex arc in order from first to last

1.Sensory receptor stimulated by change in external environment

2.Afferent neuron carries information to the CNS.

3.CNS integrates information to prepare for action.

4.Efferent neuron carries information to the effector organ.

5.Effector organ reacts to the stimulus.

What is the purpose of the stretch reflex?

Removes limb from harmful stimulus.

Example of a stretch reflex

Patellar tendon reflex.

List the steps involved in the patellar tendon reflex

1.Patellar tendon is tapped, stretching muscle and activating muscle spindles.

2.Sensory neuron carries signal to spinal cord.

3.Spinal cord integrates signal.

4.Motor neuron carries signal to skeletal muscle.

5.Quadriceps femoris contracts.

Purpose of withdrawal reflex

Removes limb from harmful stimulus.

Purpose of crossed-extensor reflex

Extensors in opposite limb contract to maintain balance.

Example of withdrawal reflex

Stepping on something sharp and pulling foot away while balancing with other leg.

List the steps involved in the withdrawal reflex

1.Painful stimulus activates sensory receptors.

2.Afferent neuron carries signal to spinal cord.

3.Spinal cord integrates information.

4.Efferent neuron carries signal to effector organs.

5.Skeletal muscles contract (injured-side flexors & opposite-side extensors).

What happens in contralateral limb during crossed-extensor reflex?

Extensors in the contralateral limb contract.

Free nerve endings (structure & example)

Neuron with dendrites in tissues; pain receptors in skin.

Encapsulated nerve endings (structure & example)

Dendrites in connective tissue; Pacinian corpuscle.

Specialized receptor cells (structure & example)

Specialized cells interpreting specific stimuli; photoreceptors.

Receptors detecting body position

Proprioceptors

Receptors detecting internal stimuli

Interoreceptors

Receptors detecting external stimuli

Exteroreceptors

Receptors detecting light

Photoreceptors

Receptors detecting chemicals

Chemoreceptors

Receptors detecting pain

Nociceptors

Receptors detecting mechanical force

Mechanoreceptors

Receptors detecting temperature

Thermoreceptors

Free nerve ending – location

Most body tissues

Free nerve ending – function

Respond to temperature and pain

Merkel discs – location

Epidermis

Merkel discs – function

Respond to light touch.

Hair follicle receptors – location

Surround hair follicles.

Hair follicle receptors – function

Detect bending/movement of hairs.

Meissner’s corpuscles – location

Superficial dermis

Meissner’s corpuscles – function

Light touch and vibration.

Pacinian corpuscles – location

Deep dermis

Pacinian corpuscles – function

Deep pressure.

Ruffini endings – location

Deep dermis

Ruffini endings – function

Detect skin stretch & joint deformation.

Special sense: smell receptor type

Chemoreceptor

Smell receptor location

Nose

Taste receptor type

Chemoreceptor

Taste receptor location

Tongue

Vision receptor type

Eye

Hearing receptor type

Mechanoreceptor

Hearing receptor location

Ear

Equilibrium receptor type

Mechanoreceptor

Equilibrium receptor location

Ear

Difference between general & special senses

General: receptors widely distributed;

Special: receptors localized to specific organs

Define olfaction

Sense of smell

Location of olfactory epithelium

Superior nasal cavity

Type of sensory neuron in olfactory epithelium

Bipolar chemoreceptor neuron

What stimulates olfactory neurons?

Odorant chemicals

Which cranial nerve carries olfactory information to the brain?

I olfactory

Which cerebral lobe contains the primary olfactory cortex?

temporal lobe

Why is smell tied to memory/emotion?

Olfactory axons project to hippocampus & amygdala

Define gustation

Sense of taste

Peg-like projections on tongue

Papillae

Structures containing gustatory receptor cells

Taste buds

Stimulus for salty taste

High Na+ concentration

Stimulus for sour taste

High H+ concentration (acids)

Stimulus for sweet taste

Monosaccharides like glucose and fructose

Stimulus for bitter taste

Varies by molecule; GPCR-mediated responses

Stimulus for umami taste

L-glutamate (amino acid)

Cranial nerves for taste

Facial (VII), glossopharyngeal (IX), vagus (X)

Brain lobe for primary gustatory cortex

Parietal lobe