Nervous System

What cells make up neural tissue?

neurons and neuroglia

Neuron

cells that generate, send, receive, and modulate signals between themselves and with other body cells

Neuroglia

cells that support and protect neurons

Major players of the nervous system

sensory receptors, central nervous system, peripheral nervous system, effectors

General somatic sensory receptors

temperature, pain, touch

Special sensory receptors

photoreceptors, mechanoreceptors, chemoreceptors, baroreceptors

photoreceptors

rods and cones

mechanoreceptors

hearing, position, balance

chemoreceptors

smell and taste

baroreceptors

blood pressure monitoring

Central nervous system

contains brain and spinal cord

functions of the CNS

process and coordinate sensory data, motor commands, higher functions of the brain

Sensory data function

receives information from internal and external environments

motor command function

control activities of peripheral organs, sends commands to muscles and glands (effectors)

higher brain functions

intelligence, memory, learning, emotion

Peripheral nervous system

all neural tissue outside of CNS and is not protected by bone

12 pairs of cranial and 31 pairs of spinal nerves, ganglia

How many cranial nerves and what do they innervate?

12 pairs; structures in the head/neck and thoracic/ abdominal viscera

How many spinal nerves and what do they innervate?

31 pairs; trunk and limbs

Neuron functions

receive, process, and transmit information

Components of a neuron

dendrite, soma, axon hillock, axon, myelin sheath, nodes of raniver, synapse

dendrite

tree like extensions at the beginning of a neuron that increase surface area of the cell body for contact with axon processes of other neurons

neurotransmitters

chemical messengers that give information from other neurons to dendrites

soma

cell body that contains nucleus and other organelles

soma function

converts chemical signal into electrical signal called an action potential

axon

elongated fiber that extends from the cell body to the terminal endings and transmits the action potential

axon hillock

site where action potentials are generated and axons arise from here

myelin sheath

fatty insulation that some axons are covered by- those covered can transmit information much faster than ones not covered

nodes of raniver

unmyelinated gaps between segments

synaptic terminals

formed by the distal end of axon branches and the terminal parts of each branch

synapse

junction of the terminal button with the dendrites of another neuron or effector

types of neruons

unipolar, bipolar, multipolar, pseudounipolar

unipolar neuron

a cell body with a single process off it which acts as both an axon and dendrite

where are unipolar neurons found

cerebellum and dorsal cochlear nucleus

bipolar neurons

cell body with one axon and one dendrite

where are bipolar neurons found

receptors in special sensory organs (sight, smell, taste, hearing)

pseudounipolar neurons

one axon that splits into 2 branches (one to CNS and one to PNS, most common for sensory neurons

pseudounipolar neurons are found in?

dorsal root ganglia, sensory ganglia of cranial nerves, and baroreceptors

multipolar neurons

cell body with multiple dendrites and one axon that can be quite long, most common in CNS, includes motor neurons and interneurons of spinal cord

neuroglia

comprise half the volume of the nervous system, preserve physical and biochemical structure of neural tissue and are essential for survival and function of neurons

What can neuroglia do that mature neurons cannot do?

divide actively and may become neoplastic

Astrocytes

form blood-brain barrier, repair, structural support, scar formation, synthesize and maintain extracellular matrix

largest among neuroglia

Oligodendrocytes

myelinate CNS axons in the white matter

most numerous of the neuroglia

microglia

involved in immune defense, phagocytosis

fewest and smallest neuroglia

ependymal cells

line central canal of spinal cord and ventricles of brain, CSF movement

3 main components of the brain

cerebrum, cerebellum, brainstem

Gray matter

outer most layer of the brain, forms cortex of cerebrum & cerebellum

How does grey matter get its grey tone?

high concentration of neuronal cell bodies

White matter

forms the bulk of the deeper parts of the brain, consists mainly of myelinated axons that connect the various grey matter areas

Where are there islands of grey matter?

inner sections of the brain, embedded in the white matter (basal ganglia and brainstem)

cerebrum

most prominent part of the brain, 2 cerebral hemispheres

What is between the 2 hemispheres of the brain?

deep fissure called the longitudinal fissure

What connects the 2 hemispheres of the brain?

thick bundle of nerve fibers called the corpus callosum

What is the major tract that the 2 hemispheres use to communicate and send info to one another?

corpus callosum

what are the 4 main lobes the cerebrum can be divided into?

frontal, parietal, occipital, temporal

sulci

grooves or depressions

gyri

ridges or elevations

What are sulci and gyri in the cerebrum used for?

larger cortical surface area within a smaller space and greater cognitive functionality is possible

central sulcus

groove that separates the frontal and parietal lobes

lateral sulcus

groove separating frontal and parietal lobes from temporal lobes

precentral gyrus

ridge directly anterior to central sulcus, location of primary motor cortex

postcentral gyrus

ridge directly posterior to central sulcus, location of primary somatosensory cortex

superior temporal gyrus

ridge located inferior to lateral sulcus, responsible for the reception and processing of sound

frontal lobe

contains the primary motor cortex which is located in the precentral gyrus

prefrontal cortex function

initiates and executes voluntary muscle movements, involved in memory, behavior, and executive functions such as decision-making, judgement, and problem solving

frontal eye field of frontal lobe

involved in initiation and execution of eye movements

broca’s area in the frontal lobe

stimulates the muscles that form words in speech

Parietal lobe

contains primary somatosensory cortex which is located in the postcentral gyrus

primary somatosensory cortex functions

conscious awareness of somatic sensations such as touch, pain, pressure, temperature, and vibrations

posterior association area of parietal lobe

located in posterior parietal lobe and extends into the occipital and temporal lobe

somatosensory stimuli, visual stimuli, and auditory stimuli meet here

What is the union of all the stimuli in the posterior association area is important for what?

proprioception and allows us to develop spatial awareness of our body position and surroundings

occipital lobe

contains primary visual cortex

primary visual cortex function

makes us consciously aware of visual stimuli

damage to occipital lobe

difficulty with locating objects in environment, identifying colors, production of hallucinations, visual illusions, word blindness, inability to recognize movement of an object

temporal lobe

contains primary auditory cortex

primary auditory cortex function

makes us consciously aware of auditory stimuli

Wernicke’s area in temporal lobe

usually in dominant hemisphere, involved in comprehension and understanding of written and spoken language

primary olfactory cortex of temporal lobe

consciously aware of smells and the olfactory association cortex helps us to process and analyze those smells

damage to temporal lobe

temporal lobe epilepsy, impaired memory skills, changes in emotional regulation and interpersonal interactions, changes in self-image and self-perception

subcortical structures

diencephalon, basal ganglia, limbic system, pituitary gland

diencephalon

located deep within the white matter of the brain, collection of 4 structures (thalamus, hypothalamus, epithalamus, subthalamus) located on either side of the midline and bilaterally to the 3rd ventricle of the brain

Thalamus of the diencephalon

relays sensory and motor information between the cerebral cortex and the rest of the brain and PNS (except smell)

Epithalamus of the diencephalon

most posterior part, consists of pineal gland

pineal body of epithalamus

participates in regulation of the body’s sleep-wake cycle through melatonin

subthalamus of the diencephalon

most ventral part, lies between thalamus and midbrain

involved in control, integration, and accuracy of motor activity

hypothalamus of the diencephalon

positioned inferioanterior to the thalamus, regulates the secretioon of hormones by the pituitary gland

Limbic system

collection of structures located in the middle of the brain

Where are the structures of the limbic system located?

lateral to the thalamus, underneath the cerebral cortex, above the brainstem

What is the limbic system responsible for?

emotional and social life, long term memory, spatial memory and navigation, motivation, olfaction, hormonal regulation

key structures of the limbic system

hippocampus, amygdala, hypothalamus, cingulate gyrus, parahippocampal gyrus, septal nuclei, mammillary body, basal ganglia

hippocampus location

medially in the temporal lobe

hippocampus is involved in

creation of short and long term memory, spatial navigation

Hippocampus damage

with severe depression it loses volume and is first area to be hit by alzheimer’s disease

amygdala nuclei is involved in

attention to an emotionally significant stimuli (happiness, sadness, anxiety), learning based on reward or punishment, and mediation of aggression

cingulate gyrus location

situated just above the corpus callosum

cingulate gyrus is involved in

processing emotions and memory, regulate motor function particularly heart rate and pressure

hypothalamus location

below the thalamus on both sides of the third ventricle

hypothalamus function

exerts control on secretion of hormones by the pituitary gland

Basal ganglia

group of interconnected subcortical nuclei

components of basal ganglia

caudate nuclei, lenticular nuclei (putamen, globus pallidus externus, and internus), subthalamic nuclei , substantia nigra

basal ganglia function

involved in motor control