The Central and Peripheral Nervous System Flashcards
Define the following terms: grey matter, white matter, tract, nerve, nucleus, ganglion, decussation, cortex,
central nervous system, peripheral nervous system, autonomic nervous system and somatic nervous system?
Grey matter = grey area of the CNS, forms the outer part of the brain and inner part of the spinal cord. Contains cell bodies and unmyelinated nerve fibres.
White matter = white area of the CNS, forms the inner part of the brain and outer layer of the spinal cord. Contains myelinated nerve fibres.
Tract = a collection of nerve fibres with the same origin, termination or function.
Nerve = a white fibre or bundles of fibres that transmit sensory sensations to the brain/spinal cord and from the brain/spinal cord to the muscles/organs.
Nucleus = a typically round structure bound by a double membrane containing genetic material. Power house of a cell.
Ganglion = a collection of cell bodies outside of the CNS (in the PNS)
Decussation = a crossed tract of nerve fibres passing through centres on the opposite side of the nervous system.
Cortex = the outer surface layer of organs
CNS = nerves and impulses occurring in the brain and spinal cord
PNS = the part of the NS that contains nerve fibres and ganglion outside of the brain and spinal cord.
ANS = the EFFERENT part of the PNS that innervates the cardiac, smooth muscles and glands. Involuntary or visceral motor system.
Somatic nervous system = consists of somatic nerve fibres that transmit impulses from the CNS to the skeletal muscles. Voluntary nervous system.
List the components of the central and peripheral nervous systems?
CNS - brain and spinal cord
PNS - everything the lies outside of the CNS, the nerves and ganglia that lie in the periphery
List the support cells of the nervous system (neuroglia) giving the function of each? (CNS ONLY)
Astrocytes = support and brace the nerves to their nutrient and blood supply, control chemical environment surrounding the nerves, control signal propagation and synapse formation.
Ependymal = CSF production and secretion. Their cilia aids in circulating CSF, cushioning the brain and spinal cord.
Oligodendrocytes = myelinate nerve fibres
Microglia = CNS macrophages that have the ability to migrate, phagocytose and clean up debris and micro-organisms as cells of the immune system are not allowed in the CNS.
List the support cells of the nervous system (neuroglia) giving the function of each? (PNS ONLY)
Satellite cells = surround cell bodies, metabolic regulation of neurons
Schwann cells = myelination of PNS nerve fibres
List the components of a neuron giving the function of each component?
Cell body = contains the nucleus and Nissl bodies. Produces proteins from the dendrites, axon and synaptic terminals. Contains ribosomes, golgi etc and provides energy and makes up the parts of the neuron.
Dendrites = act as input/receptive centres for stimulus, receive information from other neurons and dendrites and convey information towards cell bodies.
Axon hillock = arises from the cell body (neck)
Axon = arises from the Axon Hillock and ends at the terminal. It is the conducting part of a neuron, initiates impulses and transmits them towards an effector
Nodes of Ranvier = in between Schwann cells, act as regions where impules are transmitted (jumping) = faster transmission
Schwann cells = myelinated parts of an axon, increase the speed of transmission
Myelin sheath = faster conduction
Terminal branches and axon terminal = transmit signal to effector
Classify neurons as per their function and histological structure?
Multipolar neurons = have 3 or more extensions (processes) extending from the cell body, have one axon and the rest are dendrites. Function in transmitting signals from the CNS to the motor/effector organs in the periphery. Also act as interneurons between sensory and motor neurons.
Bipolar neurons = 2 processes extending from the cell body, one dendrite and one axon body on opposite side of each other. Function as receptor cells in the retina.
Unipolar neurons = single processes extending from the cell body, which splits into two, central and peripheral neuron. Function as sensory/afferent neuron that transmits sensory signals from the skin and internal organs to the CNS. Cell body lies outside of the CNS.
Describe the process of myelination?
Initially axon lies on a groove on the Schwann cell. Axon is then surrounded by the Schwann cells, the abaxonal plasma membrane is on the outer environment and the adaxonal plasma membrane is on the inner side. In between the two membranes lies the mesaxon plasma membrane. This membrane initiates myelination by extending further and wrapping around the axon.
As the Schwann cell wraps around the axon, the two sides of the Schwann cells squeeze out the cytoplasm forming tightly wrapped sheets called the Myelin Sheath.
The outer mesaxon extends from the abaxonal surface of the Schwann cell and the inner mesaxon extends from the adaxonal surface of the Schwann cell.
Describe the ventricular system?
It arises from the expansions of the lumen of the embryonic neural tube. All are connected and continuous with the central canal of the spinal cord. Filled with CSF and lined with ependymal cells (produce and secrete CSF)
Paired lateral ventricles: each one deep within each cerebral hemisphere. C - shaped chambers, connected by a septum called pellucidum.
Third ventricle: narrow and located within in the dincephalon. Connects with each lateral ventricle vis the inter-ventricular foramen.
Fourth ventricle = is connected to the third ventricle via the cerebral aqueduct, and is continuous with the central canal (spinal cord). Is dorsal to the pons and superior to the medulla. Has 3 apertures, two lateral and one medial on the roof, which connect the ventricles to subarachnoid space and fill CSF
Name the important sulci, gyri and fissures used to delineate the different lobes of the cerebral hemispheres?
gyri:
- Precentral gyres (anteriorly borders the central sulcus
- Postcentral gyres (posteriorly border the central sulcus)
Sulci:
- Central sulcus (separates the frontal and parietal lobes)
- Parieto-occipital sulcus (separates the parietal and occipital lobes)
- Lateral sulcus (separates the frontal and parietal lobes from the temporal lobes)
- Insula (deep within the Lateral sulcus and is covered by the frontal, parietal and temporal lobes)
Fissures:
- Longitudinal fissure (separates the left and right hemisphere of the brain)
- Transverse fissure (separates the cerebellum from the cerebrum below).
Describe the topographical organization from the medial to the lateral side of the primary motor and sensory
cortex that represent different body areas (motor and sensory homunculi)?
Motor:
- Medial (lower parts of the body) = knee, hip, trunk, foot, toes.
- Superior (mid parts of body) = arm, elbow, wrist, hand, fingers, thumb.
- Lateral (upper parts of body) = neck, brow, eye, mouth, tongue, face, lip, jaw.
Sensory:
- Medial (lower parts) = leg, trunk, hip, genitals, head and neck
- Superior (mid parts) = arm, elbow, forearm, hand, fingers, thumb.
- Lateral (upper parts) = eye, noses, face, lips, gums, jaw, tongue, pharynx, intra-abdominal
Identify the position of the following parts of the brain on images: the cerebral hemispheres, thalamus,
hypothalamus, internal capsule, basal nuclei, components of the brainstem, optic chiasm and pituitary gland?
Thalamus = round and middle pf brain
Hypothalamus = towards front and below thalamus
Optic chiasm = in front of hypothalamus and is small.
Pituitary = below optic chiasm and connected to anterior of hypothalamus
Pons = towards anterior side of brainstem
Midbrain = middle of brain and towards posterior side of brainstem
Medulla = small bulge below the pons, leads into the spinal cord
Internal capsule = passes between thalamus and some basal nuclei. Projection fibres.
Basal nuclei = caudate, lentiform nucleus. All 3 form the corpus striatum.
Describe the position and function of the functional areas of the cerebral cortex? (MOTOR AREAS)
Motor areas
Primary motor cortex- located in precentral gyrus of frontal lobe, function to consciously control
precise/ skilled voluntary movements of our skeletal muscles
Premotor cortex- anterior to the pre-central gyrus in frontal lobe. Controls learned motor skills of a
repetitious nature, coordinates movement of several muscle groups simultaneously b sending
activating impulses to primary motor cortex. Also used in planning movements.
Broca’s area- lies anterior to the inferior region of the premotor area- anterior to lateral sulcus.
Present in one hemisphere, usually left. Is a special motor speech area that directs muscles of the
tongue, throat and lips involved in speech production
Frontal eye lid- partially in and anterior to the premotor cortex and superior to Broca’s. Controls
voluntary movements of the eye.
Describe the position and function of the functional areas of the cerebral cortex? (SENSORY AND OTHER AREAS)
Primary somatosensory cortex- in postcentral gyrus in parietal lobe, posterior to premotor. Receive
info from sensory receptors in skin and muscles and identify part of body being stimulated- spatial
discrimination
Somatosensory association area- posterior to primary somatosensory cortex. Integrates different
sensory inputs relayed to it by primary somatosensory cortex to produce an understanding of the
object being felt
Visual areas- primary visual cortex- posterior tip of occipital cortex- receives visual info from
retina
Primary auditory cortex- superior margin of temporal lobe. Sound energy from cochlear sends
impulses to cortex where they are related to pitch, rhythm and loudness
Olfactory cortex- small areas of frontal lobes just above orbits and in medial temporal lobes
(piriform lobe) part of rhinencephalon. Conscious awareness of different odours
Gustatory cortex- in parietal lobe, perception to taste stimuli.
Vestibular cortex- posterior part of insula, conscious awareness of balance- position of head in
space
Prefrontal cortex- anterior portions of frontal lobes. Involved in intellect, complex learning, recall
and personality
Wernicke’s area- posterior to lateral sulcus- understanding written and spoken language/ sounding
out words
Lateral prefrontal cortex- language and comprehension
Name the subdivisions of the brainstem, stating the position and function of each
Midbrain-located between the diencephalon and the pons. Acts as an information highway.
Connecting the forebrain and hindbrain. Enables brain to integrate sensory info from eyes and ears
with your muscle movements (reflexes), enabling body to make fine adjustments to movements and
maintain balance and contain nuclei for cranial nerve III and IV
Pons- bulging structure wedged between the midbrain and medulla oblongata. Conduction pathway
between higher and lower brain centres, relay info from cerebrum to cerebellum, control respiratory
rate via respiratory nuclei, houses cranial nerve nuclei V, VI, VII
Medulla oblongata- most inferior part of brainstem, blends into spinal cord at foramen magnum.
Central canal of spinal cord extends into medulla and expands to form fourth ventricle. Conduction
path between higher brain centres and the spinal cord, site of decussation of tracts, houses cranial
nerve nuclei VIII, IX, X, XI, XII. Controls heart rate, by diameter, RR, vomiting, coughing, also
relays to cerebellum.
Name the subdivisions of the diencephalon, giving the function of each
Forms the central core of the fore brain surrounded by cerebral hemispheres. Consists of:
Thalamus- Afferent impulses from all senses of all parts of the body converge on the thalamus and
synapse with it. Editing process occurs in thalamus- mediates sensation, motor activities, cortical
arousal, learning and memory.
Hypothalamus-main visceral control centre of the body and NB for body homeostasis.
Autonomic control centre (control heart and breathing)
Nabila Lortan 2015
Centre for emotional response- part of limbic system, perception of pain, fear, rage, sex drive.
Body temperature regulation- thermostat for the body.
Regulation of food intake- in response to blood nutrient levels.
Regulation of water balance and thirst- release ADH.
Regulation of sleep- wake cycles- suprachiasmatic nucleus- body biological clock.
Control of endocrine functioning- induce release of hormones and produce hormones.
Epithalamus- pineal gland extends from it and secretes melatonin, sleep inducing signal. Helps
regulate sleep- wake cycle and mood, choroid plexus is also part of epithalamus which forms CSF.
