12. Peripheral Nervous System and Sensory Receptors

Flashcards covering key vocabulary and concepts related to the Peripheral Nervous System and sensory receptors.

Peripheral Nervous System (PNS)

consists of nerve cells responsible for communication to and from CNS

Afferent cells

signals into cell

Efferent cells

signals out of cell

What are the two subsystems of the PNS?

the somatic nervous system and the autonomic nervous system.

The somatic nervous system

communication between voluntary muscles actions performed by skeletal muscles

The autonomic nervous system

controls the unconscious/ involuntary body functions of the smooth muscle, cardiac muscle, and glands

How are afferent signals transmitted?

chemical, gastric, and internal mechanical stimuli

What are the parts of the SNS?

Spinal and cranial nerves

What is the function of spinal nerves?

carry sensory information into and motor commands out of the spinal cord

What is the function of the cranial nerves?

carry information into and out of the brains stem (such as all the senses)

What is the somatosensory system?

neurons and pathways that respond to both types of stimuli from the bodies surfaces and produce perception of touch, temperature, body position, and pain

Sensory receptor cells

neurons or adjacent neurons that convert physical stimuli into action potential

Location of sensory receptor cells

all over the body (skin, epithelial tissues, muscles, bones, ect)

Sensory info

processed locally in the spinal cord to reflex or sent to the brain for conscious perception of touch and proprioception

Mechanoreceptors

sense of touch or pressure or mechanical sensations

Proprioceptor

sense of relative position of the body and the strength of effort for movement

Nociceptors

sense response to harmful stimuli or pain (thermal, mechanical, chemical)

Thermoreceptors

sense changes in temperature

Chemoreceptors

sense chemical stimuli from different gasses

Photoreceptors

have a negative membrane potential change different responses to stimuli (mechanical deformation, ion channels, temperature changes, EM radiation

Mechanical deformation

stretches the membrane and opens ion channels

Chemical stimuli

open ion channels in response

Temperature changes

alters the membrane permeability

EM radiation

directly or indirectly changes membrane characteristics to allow ion transport

what happens when a receptor potential rises above threshold?

an action potential occurs in the nerve fiber

What is the relationship between threshold and the action potential

greater/increased threshold then an increase in the action potential frequency

Intensity of stimulus

info is sent to the brain by increasing the fire rate of the fiber or recruiting more sensory fibers

Spatial summation

increase in intensity will impact a larger number of sensory receptor to increase the strength of a signal

Temporal summation

increasing frequency of the nerve impulses in each fiber in response to a larger stimulus

Adaption of receptors

sensory receptors will change their response to a stimulus if it is constant

Slowly adapting receptors

also tonic receptors, rapid firing during initial contact and then slows over time

Rapidly adapting receptors

also phasic receptors, firing when stimuli starts and when it is finished and relays changes to stimuli

Timing(1)

non-adapting receptors

Timing(2)

Fast-adapting

Non-adapting

firing constantly to tell the brain something is happening

Location of receptors

the skin and muscles around the stomach/gut

Type A fibers

larger more myelinated fibers

Type C fibers

small unmyelinated fibers

Types of nerve fibers

Location of mechanoreceptors

mostly skin

what are mechanoreceptors sensitive to

magnitude or rate(frequency) of motion/force

Golgi tendon receptors

detect muscle tension indirectly via detection of stretch of the ligaments and deep tissues around the joints

Muscle spindle sensory receptors

send info to the nervous system about the length of the muscle or rate of change of length

Fast pain receptors

transmit through Aδ nerve fibers at velocities between 6 and 30 m/sec

Slow pain receptors

of pain is elicited mostly by chemical stimuli is transmitted by type C fibers at velocities between 0.5 and 2 m/sec

Free nerve endings

serve as pain receptors on the skin surface but can be in deeper tissues

Warmth receptors

warming increases AP rate, cooling decreases

Cold receptors

cooling increases AP rate during, warming decreases

Adapting for thermoreceptors

slow

what else can thermoreceptors respond to?

chemicals

Graphical representation of thermal receptors

what does the distance chemoreceptor type do?

receive stimuli in gases in the olfactory system

what does the direct chemoreceptor type do?

detect stimuli in liquids include the taste buds in the gustatory system

Anterior half of the parietal lobe

used for reception and low-level interpretation of somatosensory signals

Posterior half of the parietal lobe

provides higher levels of interpretation

Exceptions

are visual signals terminate in the occipital lobe and auditory signals terminate in the temporal lobe

From right to left of signals

Sensory signals from the right side of the body terminate in the left side of the brain and visa versa

Anterior half of the parietal lobe

used for reception and low-level interpretation of somatosensory signals

Posterior half of the parietal lobe

provides higher levels of interpretation

Somatosensory area I

high degree of localization of the different parts of the body, most important of two parts

Somatosensory area II

poor localization

Sensory Cortex Homunculus

map of brain areas dedicated to sensory processing for different body parts

Multiple Cerebro-Spinal Sclerosis (MS)

an autoimmune disease resulting in damage to myelin covers (i.e., glial scars) of nerve cells in the white matter of the brain and spinal cord

Effects of MS

disrupts the nervous system's ability to transmit signals, resulting in a range of signs and symptoms

MS Physical symptoms

as double vision, vision loss, eye pain, muscle weakness, and loss of sensation or coordination, mental symptoms, and sometimes psychiatric problems

Causes of MS

either destruction by the immune system or inactivation of myelin-producing cells