nervous system basics

central nervous system (CNS) contains

• peripheral nervous system

• autonomic nervous system

• brain + spinal cord

CNS function

• receiving and processing sensory information

• relaying information to muscles and glands

• creating appropriate responses

• coordinates emotions, memory, cognition, and learning

what is cerebral spinal fluid (CSF)

• maintains homeostasis, delivers nutrients and carries away waste

• reabsorbed through arachnoid villi

• produced by the choroid plexus

what are the meninges

• sticks the brain to the skull so that the brain is suspended and supported

• 3 layers: dura mater, arachnoid mater, and pia mater

dura mater

• outermost layer; thick, tough, collagenous; protects soft brain tissue

arachnoid mater

• middle layer; thin, delicate, semitransparent

• weblike trabeculae creates subarachnoid for CSF flows

pia mater

• very thin, attached to the brain, follows every contour (sulcus and gyrus

what is the blood brain barrier (BBB)

• regulates what substances can get from bloodstream into tissue fluid of the brain

• maintained by astrocytes

• inflammations affects the permeability

blood supply: anterior circulation

• internal carotid arteries

blood supply: posterior circulation

• vertebral arteries

blood supply: circle of willis

• ring of vessels that unites anterior and posterior circulation at base of the brain

parts of the brain

• cerebrum (cerebral cortex, basal ganglia, limbic cortex, & corpus callosum)

• diencephalon (thalamus & hypothalamus)

• cerebellum

• brainstem (midbrain, pons, & medulla)

lobes of the brain

• frontal, parietal, temporal, & occipital

• located in the cerebrum

frontal lobe

• involved in complex thought, motivation, morality, & speech

• broca area: expressive language

• contains motor cortex

parietal lobe

• contains the somatosensory cortex

• limbic area: memory & emotions

temporal lobe

• contains auditory, vestibular, & parts of the language center (balance & hearing)

• wernicke area: respective language

occipital lobe

• contains visual cortex (vision)

limbic system

• part of the cerebrum that is most closely associated with emotion & memory

• olfaction occurs here (smell & memory)

basal ganglia

• involved in initiation, coordination, & execution of movement; control of skeletal muscles

diencephalon parts & function

• deep in the brain; connects upper brainstem (midbrain) and cerebral hemisphere

• thalamus, hypothalamus, & epithalamus

thalamus

• processes and relays information

• involved in the execution of motor functions

• emotion, language, creativity, and complex thought

hypothalamus

• regulatory center for the autonomic nervous system

• regulates sleep, body temp, appetite, & sex drive

epithalamus

• contains the Pineal gland which is thought to be important in regulating circadian rhythms in response to light-dark cycles

cerebellum

• coordinates smooth movement and maintains posture and balance

• compares the desired motor program with the moment-to-moment execution of the movement and instantaneous adjustments to improve the match (so you don’t trip going up the stairs again)

• lateral hemispheres involved in planning and programming voluntary movements

• lesions of the cerebellum result in ataxia (impaired balance), failure of rapid movement

brainstem

• critical for transmission of impulses between the brain and spinal cord

• midbrain, pons, & medulla

midbrain

• cerebral peduncles: contains motor tracts to spinal cord

• superior colliculus: visual attention; tracking moving objects

• inferior colliculus: hearing attention; tracking sound in space

pons

• reticular formation: sleep, respiration, & posture

medulla

• cardiac, vasomotor, & respiratory centers

reticular activating system

• maintains consciousness and alertness traverses through the brainstem to the thalamus. also referred to as the “arousal system”

anatomy of spinal cord

• butterfly pattern of gray matter surrounded by white matter called horns (gray matter made of neuron cell bodies for receiving sensory & motor signals)

• dorsal horn: sensory neurons

• ventral horn: motor neurons

• lateral horn: sympathetic neurons

spinal tracts

• posterior (dorsal) columns: ascending sensory

• anterior (ventral) columns: descending motor

• lateral columns: mix of both

spinal nerves

• dorsal roots: carry sensory information from somatic receptors to neurons in the posterior horn (collects in the dorsal root ganglion)

• ventral roots: contain motor neurons that originate in the anterior horn and travel in the spinal nerve to skeletal muscles

autonomic nervous system

• composed of neurons in the CNS and PNS that mediate automatic or involuntary functions

• has sensory afferents and motor efferents

• preganglionic neurons: emerge from the spinal cord

• postganglionic neurons: traveling to the target cell

parts of neurons

• dendrites: receive signals & transmit them to soma

• soma: cell body; processes excitatory & inhibitory postsynaptic potential

• axon: generates & conducts action potentials

CNS neuroglia cells

• astrocytes

• oligodendrocytes

• ependymal cells

• microglia

astrocytes

• most abundant

• forms supportive framework to create the BBB

oligodendrocytes

• form myelin sheaths in CNS that speed signal conduction

ependymal cells

• lines brain; secrete and circulate cerebrospinal fluid (CSF)

microglia

• develop from white blood cells (monocytes) and become concentrated in areas of damage to clean up debris

PNS neuroglia cells

• schwann cells

• satellite cells

schwann cells

• form myelin sheath in PNS; assist in regeneration of damaged fibers

satellite cells

• regulate the chemical environment of the neurons

depolarization

• when neurotransmitters bind to receptors on dendrite and cell body; allowing cations (mainly Na+) to leak in (positive membrane charge)

action potential

• change in membrane potential is enough to reach threshold

repolorization

• efflux of potassium ions (voltage-gated potassium channels)

EPSPs

• excitatory signals that result from the influx of positive ions (Na+, Ca2+, etc.)

IPSPs

• inhibitory signals that result from influx of negative ions (Cl-) or efflux of potassium (K+)

speed of action potential determined by

• axonal diameter & myelination

continuous conduction

• continual depolarization of the membrane in unmyelinated axons

saltatory conduction

• jumping of AP from Node to Node in myelinated axons

neurotransmitters: amines

• Noradrenaline (NE), Dopamine (DA), Serotonin

• regulate thought process and mood

neurotransmitter: amino acids

• glutamate (excitatory); GABA (inhibitory)

• glutamate is involved in memory

sensory function

• activates specialized sensory receptors & thalamus

motor function

• interaction among the basal ganglia, cerebellum, & cortex

• transmitted from the primary motor cortex down the corticospinal tract

• corticospinal tract: controls distal muscles of the arms and legs

• vestibulospinal, reticulospinal, and tectospinal tracts: controls proximal muscle groups & axial muscles

consciousness

• awareness of the surroundings and one’s own thoughts and sensations

• α waves: search and retrieval

• θ waves: memory encoding tasks

memory

• synaptic phenomenon in which neurons in the memory trace or circuit alter the efficiency of synaptic transmission

• short-term memory: result of short-term alterations or presynaptic neurons

• long-term memory: result of permanent changes in the postsynaptic neurons

sleep

• state of decreased arousal from which a person is easily awakened

• α waves: occurs during relaxed state with the eyes closed

• β waves: occurs during visual stimulation & active problem solving (REM)

• θ and δ waves: occurs during deep sleep