Somatic Nervous System

What is the somatic nervous system involved in? What is the exception?

voluntary control of body movements; exception of reflex arcs

What are afferent nerves involved with?

reception of internal and external stimuli such as touch, heat, pain, hearing, and sight

What is incoming information coordinated by to achieve skilled motor programs?

spinal cord, somatomotor cortex, and cerebellum

How do efferent nerves cause contraction?

transmit impulses from CNS to skeletal muscles

What components make up the somatic nervous system?

sensory receptors, sensory neurons (PNS), motor neurons, spinal cord/brain (CNS), skeletal muscle

What is the signal transduction route in the sensory division?

sensory input to CNS; spinal cord initiates voluntary motor control and sends info to brain; CNS sends response to contract muscles

What is the signal transduction route in the motor division?

spinal cord initiates response via lower motor neurons OR upper motor neurons of somatomotor cortext and brain stem pathways make contact with low motor neurons; somatomotor cortex initiate voluntary movement and modulate muscle or reflex activity

Simple Reflex Arc

neural pathway that mediates a reflex action

Where do sensory inputs pass directly? Why?

synapse in in the spinal cord; allows reflex actions to occur relatively quickly by activating spinal motor neurons without the delay of routing signals through the brain

When does the brain receive sensory input during a reflex?

while the reflex action occurs

What are the neural connections in a CNS reflex?

sensory receptor, sensory neuron, brain or spinal cord, interneuron, motor neuron, effector organ

What is the sequence of events in a patella reflex?

tap/bend patellar tendon; stretch receptors in muscle stimulated; sensory neuron in muscle send signal to spinal cord; spinal cord detects signal and sends response; motor neuron carries response to muscle from spinal cord; quadriceps muscle contracts

What does the somatic nervous system rely on to respond to internal and external stress?

receptors

What are some sensory receptor examples?

golgi tendon organs, muscle spindles, Meisner's corpuscles, Merkel's disks, Pacinian corpuscle, Ruffini corpuscle, free nerve endings, nerve endings in joints, Krause's corpuscle

What divisions of the nervous system are responsible for reflexes?

somatic, autonomic

What part of the CNS determines balance?

cerebellum

What divisions of the nervous system are also part of the somatic nervous system?

CNS, PNS, afferent/sensory, somatic sensory, efferent/motor, somatic nervous

If you pinch a dog's toe, how is that signal transmitted?

sensory neurons bring info to spinal cord, to motor neurons back to limb

Where do pain signals go?

both brain and spinal cord, but spinal cord provides initial point of action

What is the functional unit of the nervous system?

neuron

What is a nerve?

an aggregation of a bunch of neurons to transmit information

What is a simple reflex?

a reflex action involved in quick movement of limbs or body parts

Why does the spinal cord act on its own during a reflex?

reflexes are very quick and sharp; if signal has to go to brain, it may be too late

What is a receptor?

a cell or cell type that receives a special modality or sensation

In order to mediate pain, what does a neuron need?

to be a receptor to receive stimulation and connect the information to the neuron

On what part of the spinal cord are sensory neurons always found?

dorsal aspect

Describe the patella reflex.

when the patella tendon is tapped, the tendon and muscle are stretched; the receptors in the muscle sense the stretch; the stretch is mediated through nerve to spinal cord, causing the muscle to contract and extend leg

What are some reasons why the patella reflex may not work?

femoral nerve damaged, receptors not responsive, spinal cord damaged, muscle fatigue, sciatic nerve damaged, brain suppressing reaction

Where are golgi tendon organ receptors found?

tendons

Where are muscle spindles receptors found?

muscles

Where are Meisner's corpuscles receptors found?

skin, for light touch

Where are Merkel's disks receptors found?

skin, for touch and texture

Where are Pacinian corpuscle receptors found?

skin, for pain and deep pressure

What do Ruffini corpuscles sense?

stretch and kinesthesia

What do free nerve endings sense?

pain

What do nerve endings in joints sense?

position

What do Krause's corpuscles sense?

cold sensation in conjunctiva

What sensory receptors are in the skin?

Meisner's corpuscles, Merkel's disks, Pacinian corpuscle, Ruffini corpuscle

What sensory receptors are in the muscular system?

golgi tendon organs, muscle spindles

How are muscle spindles receptors different from golgi tendon organs?

muscle spindles do not have contractile elements in the middle so they don't contract