Peripheral nervous system- sensory division

what is the peripheral nervous system made up of?

it is made up of sensory and motor neruro’s, bundles into nerves

what is the role of the peripheral nervous system?

role is to take information to and from the central nervous system. going to muscles and glands

what is the ganglia?

this sits outside the central nervous system and is clusters of nerve cell bodies

what sits inside the dorsal ganglia?

cell bodies of the sensory neurons

how many pairs of spinal nerves are there?

31 pairs of spinal nerves, which arise from the spinal cord.

what kind of nerve fibres are in a spinal nerve?

all are mixed nerves containing both sensory and motor fibres

what are the two roots in the spinal cord?

the dorsal root and the ventral root

what is in the ventral root?

contains axons of motor neurons (there is no ganglia in this root as the the motor nerve cell bodies are in the grey matter of the spinal cord)

why are the nerve cell bodies of motor neurons in the grey matter of the spinal cord?

because the neuron for a motor neuron is a multipolar neuron, and the cell body does not have any myelin, therefore it sits in the grey matter

what is the dorsal root?

is what contains the axons of the sensory neurons.

what is closer to the front of the body ventral or dorsal root?

ventral

why does the dorsal root have a ganglia?

because the sensory neurons are bipolar, meaning the cell body is in the middle of the bipolar neuron (the ganglia houses the cell body of the neuron)

what is a nerve?

bundles of neurons with nerve fibres arranged into the nerve

where do nerves arise from?

they arise from the central nervous system (brain and spinal cord)

how many airs of cranial nerves?

12 pairs

what are some examples of cranial nerves

the olfactory, optic, facial, accessory etc…

what the of nerves are cranial nerves?

most are mixed nerves, i.e they contain both sensory and motor nerves

what does it mean is a nerve is mixed with motor and sensory nerve fibres?

means that nerves contain fibres that carry impulses to the brain, as well as fibres that carry impulses away from the brain

few cranial nerves…

cary only sensory impulses or motor neurons

where do cranial nerves connect to the brain?

they feed through the brain base- then can connect to the brain

are sensory neurons part of afferent or efferent division?

afferent

what is a receptor?

a structure that is able to detect change in bodies internal or external environment

what is the pathway of the sensory peripheral nervous system?

the body will receive signals at receptors or sensors. the stimulated receptors send singnals to sensory neurons. the signals are hen passed to the central nervous system to be intergrated and acted upon.

what are visceral sensory neurons?

neurons which bring impulses from internal organs. for example feeling hunger in the stomach.

what are somatic sensory neurons?

neurons which bring impulses from the skin and muscles

different receptors are able to detect…

different stimuli

what is a sense organ?

is when receptor cells of a particular type are grouped together.

Explain the eye sense organ

rod and cone cells in the retina are stimulated by light and transmit signals via the optic nerve to the brain.

Explain the ear sense organ?

the cochlea contains fluid and fine hair like sensors that detect sound waves. they transmit signals to the Brian via the auditory nerve. Also the vestibular system is a series of canals and specilalised sensory cells that detect the position of the head (maintains balance). these signals are sent to the Brian via the vestibular nerve

explain the nose sense organ

specialised cells in the nasal cavity send signals to the brain via the olfactory bulb and the olfactory nerve.

explain the taste sense organ

specialised cells within the epithelium of the tongue send signals via facial nerve and other fibres

explain the touch sense organ

specialised cells in the skin can detect; heat (from the thermoreeptors), light pressure, pain, cold and strong pressure. the touch sense will send signals via the sensory nerves to the central nervous system

what is proprioception?

receptors located in muscles and joints provide information about body positioning

what are baroreceptors?

they are receptors that decide blood pressure, these are in the carotids and aortic arch

what are osmoreceptors?

receptors that monitor water homeostasis . they are highly sensitive to small changes in osmotic pressure

what is osmotic pressure determined by?

the concentrations of substances dissolved in the water of the blood plasma

where are osmoreceptors located in the hypothalamus?

they are located in the hypothalamus

what do osmoreceptors do?

they stimulate the hypothalamus so that the body’s water content is maintained within a very narrow limit

what are chemoreceptors

receptors that are stimulated by particular chemicals.

where are chemoreceptors located and what do they do?

they are present in the nose and mouth giving sensitivity to tastes and odours. there is also chemoreceptors internally which are sensitive to body fluids. there are also chemoreceptors in blood vessels (aorta and carotids) that are sensitive to the PH of blood and oxygen and carbon dioxide concentrations- these receptors are also involved in the regulation of heartbeat and breathing

what are thermoreceptors?

they are receptors that respond to hot and cold.

where are thermoreceptors and what do they do?

skin receptors inform the brain (hypothalamus and the cerebrum) of changes in the outside temperature. therfore we are consciously aware of the temperature in our surroundings

what does the hypothalamus do in response to thermoreceptors

it regulates the temperature

what does the brain (cerebrum) do in response to messages from thermoreceptors?

allows the person to have a conscious perception of temperature

peripheral thermoreceptors in the skin are…

nerve endings

what is core temperature and how is it regulated?

is the temperature inside the body. it is monitored by thermoreceptors in the hypothalamus. the hypothalamus detects the temperature of the blood flowing through the Brain and using information received from thermorecpetors in skin and its own thermoreceptors the hypothalamus can regulate body temperature

what is another name for touch receptors?

also known as mechanoreceptors or pressure receptors.

where are touch receptors mainly found

in the skin. some are very close to the skin (and therefore are sensitive to light touch in areas such as the lips, fingertips, eyelids and the external genital areas). other touch receptors are located deeper and are sensitive to pressure and vibrations

touch receptor nerve endings are associated with…

the base of each hair follicle, therfore they respond to any light touch that bends the hair.

do touch receptors close to the skin adapt rapidly?

yes, that’s why after a short time we are no longer aware of the clothes touching our bodies.

how are pain receptors stimulated?

by damage to the tissues, for example a cut, bump, poor blood flow to a tissue, or excessive stimulation for stimuli such as heat or chemicals.

where are pain receptors especially concentrated?

in the skin and mucous membranes

in what organs are there pain receptors?

occurs in most organs (but not the brain)

how are pain receptors different to other receptors?

unlike many other receptors, pain receptors adapt little to none at all. therefore pain continues as long as a stimulus is present. in some cases prolonged stimulation makes pain worse.

why are pain receptors neccesarry ?

they are important because pain warns us that damage to tissues is occurring. pain receptors failing to adapt warns us about a tissue damaging situation