Chapter 14: Nervous System

Integration of Nervous System Functions

Study of how the nervous system processes sensory input, produces responses, and stores information

Sensation

Process initiated by stimuli acting on sensory receptors

Perception

Conscious awareness of sensations

Senses

Means by which the brain receives information about the environment and body

General senses

Widely distributed throughout the body

Special senses

Located in specialized organs (smell, taste, vision, hearing, balance)

Somatic senses

Touch, pressure, temperature, proprioception, and pain

Visceral senses

Pain and pressure from internal organs

Generator potential

Graded potential in general sensory receptors that leads to action potentials

Receptor potential

Graded potential in special sensory receptors that leads to neurotransmitter release

Mechanoreceptors

Detect compression, bending, stretching; involved in touch, pressure, proprioception, hearing, balance

Chemoreceptors

Respond to chemical binding; involved in smell and taste

Thermoreceptors

Detect temperature changes

Photoreceptors

Respond to light (vision)

Nociceptors

Detect extreme mechanical, chemical, or thermal stimuli (pain)

Cutaneous receptors

Sensory receptors located in the skin

Visceroreceptors

Sensory receptors associated with internal organs

Proprioceptors

Sensory receptors in joints and tendons that detect stretch and body position

Free nerve endings

Simple sensory receptor type that detects pain and temperature

Merkel disk

Receptor for light touch, slow adapting

Hair follicle receptor

Detects hair movement

Pacinian corpuscle

Detects deep pressure and vibration, rapidly adapting

Meissner corpuscle

Detects light touch, rapidly adapting

Ruffini end organ

Detects skin stretch, slow adapting

Muscle spindle

Detects muscle length and stretch; involved in muscle tone and stretch reflex

Golgi tendon organ

Detects tension in tendons

Graded potential

Change in membrane potential due to stimulus interaction with receptor

Primary receptor

Sensory receptor whose axon generates action potentials directly

Secondary receptor

Sensory receptor that releases neurotransmitters to stimulate a neuron

Primary receptor example

Pacinian corpuscle generating action potentials directly

Secondary receptor example

Taste cell releasing neurotransmitter to sensory neuron

Threshold

Level at which a receptor potential triggers action potentials

Central nervous system (CNS)

Brain and spinal cord where sensory signals are processed

Adaptation

Reduced sensitivity to a continuous stimulus

Tonic receptors

Slow-adapting receptors that respond to continuous stimuli

Phasic receptors

Rapidly adapting receptors that respond to changes in stimuli

Pain

Unpleasant sensory and emotional experience triggering autonomic, psychological, and motor responses

Fast pain

Sharp, localized pain carried by large myelinated axons

Slow pain

Diffuse, burning or aching pain carried by small less-myelinated axons

Referred pain

Pain perceived in a location different from the source

Cause of referred pain

Convergence of organ and skin inputs onto the same spinal neurons

Chronic pain

Persistent pain not directly linked to immediate tissue injury

Chronic pain causes

Arthritis, migraines, back pain, or unknown causes

Emotional effects of chronic pain

Depression, frustration, helplessness, hopelessness

Primary sensory areas

Cortical regions that receive sensory input

Primary somatic sensory cortex

Located in postcentral gyrus; processes touch, pressure, pain, temperature

Taste area

Located in the insula

Olfactory cortex

Located on inferior surface of temporal lobe; processes smell

Primary auditory cortex

Located in temporal lobe; processes hearing

Visual cortex

Located in occipital lobe; processes vision

Primary motor cortex

Controls voluntary movement; contains ~30% of upper motor neurons

Premotor area

Plans and organizes motor movements

Prefrontal area

Responsible for motivation, planning, emotional behavior, and mood

Working memory

Short-term storage used to perform immediate tasks

Short-term memory

Lasts minutes to days; involves long-term potentiation

Long-term memory

Lasts days to lifetime; involves consolidation

Consolidation

Process of strengthening synaptic connections to form long-term memory

Declarative (explicit) memory

Memory of facts; involves hippocampus and amygdala

Procedural (implicit) memory

Memory of skills; involves cerebellum and premotor area

Memory processing

Conversion of short-term memory into long-term memory

Long-term potentiation

Strengthening of synapses during memory formation

Protein synthesis in memory

Increases size and number of synaptic connections

Dendritic spikes

Structures where new synapses form during memory consolidation

Cytoskeleton changes

Structural neuron changes that make memory more permanent

Stimulus intensity encoding

Determined by frequency of action potentials

Cold stimulus example

Activates thermoreceptors

Olfaction receptor type

Primary receptor (generates action potentials)

Hearing receptor type

Secondary receptor (releases neurotransmitter)

Fading smell of perfume

Example of adaptation

Below-threshold stimulus

Produces receptor potential but no action potential

Proprioceptors location statement

False—associated with joints/tendons, not visceral organs

Secondary receptor communication

Does not directly send signals to brain (uses neuron)

Phasic vs tonic adaptation

Phasic receptors adapt faster than tonic receptors