brain and nervous system Flashcards
(51 cards)
white matter
myelinated axons (nerve cell fibres) which connect various grey matter areas of the brain to each other. they carry nerve impulses between neurones. found in the central part of the brain, appearing darker on CT and lighter on MRI.
grey matter
nerve cell bodies and unmyelinated axons. handles muscle control and sensory perception such as seeing, hearing, memory, emotions, speech, decision making and self-control. appears more white on CT, and darker on MRI
cerebral cortex (grey matter)
made of multiple folds and grooves known as sulci (small inlets between the folds containing CSF) and gyri (folds in the cortex), increasing the surface area.
cerebrum
largest part of the brain occupying the anterior and middle cranial fossae. divided by a deep cleft called the longitudinal cerebral tissue. this separates the cerebrum into a right and left hemisphere, each contains a lateral ventricle . hemispheres are connected by a mass of white matter called the corpus callous
cerebellum
motor control. coordinations of voluntary muscular movement, posture and balance. damage to cerebellum causes clumsy uncoordinated muscular movement, staggering gait and an inability to carry out steady and precise movements.
midbrain and brainstem
critical functions such as cardiac and respiratory. motor and nerve supply to face and neck. regulates the CNS and facilitates motor / sensory nerve pathways from the rest of the body. consists of the thalamus and midbrain with the brainstem containing the pons, medulla oblongata and spinal cord.
meninges
brain and spinal cord surrounded by 3 layers of tissue. these lies between the skull and the brain and between the vertebral foramina and the spinal cord. made of (outside to in): dura, arachnoid then Pia mater
dura mater
made up of 2 layers of dense fibrous tissue. inner surface of skull and protective covering for the brain. forms the falx cerebri, falx cerebelli and tentorium cerebelli.
arachnoid mater
delicate alter. CSF flows in the subarachnoid space. arachnoid villi in venous sinuses allow CSF to exit subarachnoid space and enter the bloodstream.
pia mater
impermeable to fluid. works with other dura to protect and cushion the brain. allows passage of blood vessels to brain.
ventricles of the brain
main function is to create and circulate CSF.
lateral ventricles
located within the cerebral hemispheres. one on each side of MSP. inferior to corpus callous. communication with 3rd ventricle by inter ventricular foramen. has anterior/posterior horn and inferior horn. each ventricle has a choroid plexus, often calcified on CT, as is the pineal glands
third ventricle
located in the midbrain. inferior to lateral ventricles. between 2 parts of the thalamus. communicated with fourth ventricle by the cerebral aqueduct
fourth ventricle
diamond shaped. located in the brain stem. situated inferior and posterior to the third ventricle. between cerebellum and pons. continuous with central canal of the spinal cord. communicated with subarachnoid space by foramina superiorly
what is CSF?
created in the choroid plexus in the lateral ventricles. protects and cushions the brain, and allows for nutrient delivery. fluid contained in the central canal of spinal cord, subarachnoid space and cerebral ventricles. clear alkaline fluid.
absorption of CSF
mostly absorbed by arachnoid villi on the arachnoid mater into the dural (venous) sinuses. the absorption is determined by the pressure differences on each side of the villi walls. increased CSF pressure, decreased venous pressure = CSF passes into blood. increased venous pressure, decreased CSF pressure = arachnoid villi collapse preventing passage of blood constituents into CSF
the blood brain barrier
semi-permeable. oxygen and carbon dioxide pass quickly across the barrier. larger molecules pass more slowly from the blood to the brain. maintains constant environment (homeostasis) for the neurones in the CNS. protects the brain from potential toxins in the blood, although this also means antibodies/antibiotics are usually unable to pass through. prevents the escape of neurotransmitters from the CNS into general circulation.
what affects the permeability of the blood brain barrier
hypertension, development, microwaves, infection, trauma, schema, inflammation and raised intracranial pressure
functions of the nervous system
detects and responds to changes inside and outside of the body. works with the endocrine system to control important aspects of body function and maintain homeostasis. nervous system provides immediate short-acting responses whilst endocrine is usually slower and more prolonged
motor divison
voluntary = somatic nervous system, movement of voluntary (skeletal) muscles
involuntary (split further) = autonomic nervous system, functioning of smooth muscle, cardiac muscle and glands
involuntary / autonomic nervous system
sympathetic = controls body’s response during perceived threat fight or flight, originates in spinal cord, shuts down responses not critical to survival
parasympathetic = controls body’s response while at rest, originates in spinal cord and medulla, restores body to state of calm
nervous tissue
neurones responsible for sending impulses to other parts of the body. glial cells support cells insulate, protect and support neurones:
astrocytes - star shaped, control the blood brain barrier
oligodensrocytes - support and insulate axons
microglia - immune defence cells
ependymal cells - CSF production
neurones
cells which make up nerve tissue, supported by a special connective tissue called neuroglia (glial cells), need a continuous supply of oxygen and glucose to survive
function of a neurone
- receive sensory input
- interpret this signal and decide how to response
- effect a response
