BIOL 2111-02 Chapter 13: Peripheral Nervous System

Sensory receptors, nerves, and ganglia

PNS includes all structures OUTSIDE the brain and spinal cord… (list the structures)

Sensation

(definition) body AWARE of change (stimuli) in the environment

Perception

(definition) conscious INTEGRATION of stimuli (cerebrum and cortex)

Sensory Receptors

(definition) Structures SIGNAL/SENSE changes in the environment

Transduction

Convert one form of energy to another form (aka nerve impulses)

Mechanoreceptors

(receptor) Generates nerve impulses when deformed by mechanical stimuli

Thermal Receptors

(receptor) Sensitive to changes in TEMPERATURE

Chemoreceptors

(receptor) Responds to CHEMICALS (example: blood chemistry)

Photoreceptors

(receptor) Responds to light for VISION in retina

Proprioceptors

(receptor) Responds to INTERNAL STIMULI (determines body location in an environment)

Nociceptor

(receptor) Responds to DAMAGING STIMULI, resulting in PAIN.

Nerve

(definition) Cordlike ORGAN consisting of parallel bundles of PERIPHERAL AXONS

Amitotic

Matured neurons are considered…

Amitotic

Another word for “no mitosis” …

Regenerate

Unlike CNS axons, PERIPHERAL AXONS (cell body is INTACT) can…

Do not regenerate

Unlike PNS axons, CNS AXONS…

Paralysis

(definition) CNS axons DO NOT regenerate, because CNS oligodendrocytes bear growth-inhibiting proteins which leads to…

Paraplegia

(definition) Occurs in SPINAL CORD BETWEEN T1-L1, results in loss of function (motor and sensory) in the LOWER LIMBS

Quadriplegia

(definition) Occurs in CERIVAL SPINAL CORD, results in loss of function (motor and sensory) in ARMS and LOWER ARMS

Sensory, Motor, Mixed

Nerve Classifications (3 types)

Sensory

Nerve Classification: AFFERENT (arrival) AXONS

Motor

Nerve Classification: EFFERENT (effector) AXONS

Mixed Axon

Nerve Classification: AFFERENT AND EFFERENT AXONS

Brain and Brain Stem

Nerve Location: Cranial

Spinal Cord

Nerve Location: Spinal

12 Cranial Nerves

How many cranial nerves are found in the PNS?

Olfactory (I), Optic (II), Vestibulocochlear (VIII)

Which cranial nerves are classified as SENSORY ONLY?

Oculomotor (III), Trochlear (IV), Abducens (VI), Accessory (XI), Hypoglossal (XII)

Which cranial nerves are classified as MOTOR ONLY?

Trigeminal (V), Facial (VII), Glossopharyngeal (IX), Vagus (X)

Which cranial nerves are classified as MIXED?

31 Pairs of Spinal Nerves

How many pairs of spinal nerves arise from the united dorsal and ventral root?

mixed nerves

(nerve classification) ALL spinal nerves are considered…

Dermatome

(definition) Area of the SKIN innervated by the cutaneous branches of a SINGLE spinal nerve

Reflex

(definition) Unlearned, rapid, AUTOMATIC, and predictable motor responses to a stimulus. They occur WITHOUT the INVOLVEMEN OF THE BRAIN, but can be modified by the brain.

Reflex Arc

Reflexes occur over highly specific NEURAL PATHWAYS called…

Receptor, Sensory Neuron, Integration Center, Motor Neuron, Effector

List the components of a Reflex Arc (start → finish)

Receptor

(Reflex Arc) ACTIVATED by a stimulus…

Sensory Neuron

(Reflex Arc) Sends AFFERENT impulse to CNS…

Integration Center

(Reflex Arc) THE CONTROL CENTER… A CNS synapse / interneuron…

Effector

(Reflex Arc) The MUSCLE FIBER/GLAND which produces a response…

Stretch and Golgi Tendon Reflex

(Types of Reflexes) Golgi Tendon (sensory receptors) is activated by a stretch, which stimulates the muscles to contract and antagonist muscle to relax.

Stretch and Golgi Tendon Reflex

(Types of Reflexes) Functions to maintain muscle tone in large POSTUR(e)al muscles and help prevent damage due to excessive STRETCH.

Flexor (withdrawal) Reflex

(Types of Reflexes) Initiated by a PAINFUL stimulus that causes AUTOMATIC WITHDRAWL of the threatened body part from the stimulus (ipsilateral and polysynaptic)

Crossed Extensor Reflex

(Types of Reflexes) Consists of an ipsilateral flexor reflex and a contralateral extensor reflex. Function → Maintains Balance