Structure and function of the neuro system Flashcards
Skull
- consists of 22 bones
- adult skull bones are fused together by sutures and immovable fibrous joints
- foramina (base of skull) allow nerves and blood vessels to transmit between body and brain)
- Foramina magna-spinal cord exits the brain
Efferent pathways of PNS
-Descending; innervate effector organs
Afferent pathways of PNS
-Ascending; sensory to spinal column
Spine
- provides attachment for large muscles
- 24 verebral bones, separated by intervertebral disks and supported at the base of the sacrum
- sacrum: made of 5 fused vertebrae and ends in the coccyx
Peripheral Nervous System (PNS)
- Somatic nervous system
- autonomic nervous system
- sympathetic
- parasympathetic
Brain and brain stem
body’s control center consisting of cerebral hemispheres, cerebellum, brain stem, thalamus, basal ganglia all enclosed in meninges
-divided into three regions: forebrain, midbrain, hindbrain
Somatic Nervous System
- Part of the PNS
- Motor and sensory pathways regulate voluntary motor control of skeletal muscle
Autonomic Nervous system
-motor and sensory pathways regulate the body’s internal environment through the involuntary control of organ systems
Neurons
- primary info and communication cell
- variable size and structure throughout the nervous system
- some continue to divide (olfactory) and some die off as not needed
- contain: microtubules (transport), neurofibrils (structural support), missi substances (protein synthesis)
Spinal cord
- brain and spinal cord together form the CNS
- Cauda equina: bundle of nerve roots, located at the base of the spinal column, that connect to the legs, bladder, bowels, and genitals
Components of neuron: Cell body (soma)
Cell body
- located mainly in CNS
- Nuclei: densely packed cell bodies in CNS
- Ganglia and plexuses: groups of cell bodies in the PNS
Components of neuron: dendrites
Dendrites
- receptive portion of the neuron: sends impulses to the cell body
- Dendritic zone: is the receptive portion of the neuron that receives a stimulus and continues further conduction
Cranial nerves
-emerge from brain
-12 cranial nerves
1-olfactory
2-optic
3-oculomotor
4-trochlear
5-trigeminal
6-abducens
7-facial
8-vestibulocochlear nerve
9-glossopharyngeal
10-vagus
11-accessory
12-hypoglossal
Components of neuron: axon
AXON
- -carry nerve impulses away from cell body
- action potentials begin at axon hillock
- myelin
- endoneurium
- neurilemma (schwann sheath)
- nodes of ranvier
- saltatory conduction
- divergence
- convergence
Three components of neuron
- cell body-soma,
- dendrite
- axon
Myelin (axon)
- segmented layer of lipid material insulating substance
- myelin sheath: entire membrane
- formed and maintained by the schwann cell
Schwann cell (axon)
-thin membrane between the myelin sheath and the endoneurium
saltatory conduction (axons)
-causes faster transmission by allowing ions to flow between segments of myelin rather than along the entire length of axons
Sensory neurons
- transmit impulses from peripheral sensory receptors to the CNS
- Are transmitted via an afferent pathway
Associational or interneurons
-transmit impulses from neuron to neuron
motor neurons
- Transmit impulses from the CNS to an effector organ
- transmitted via an efferent pathway
Neuroglia
- Support the neurons of the CNS
- astrocytes
- oligodendroglia
- microglia
- Ependymal
Astrocytes
-fill the spaces between neurons and surround the blood vessels in the CNS
Oligodentrocytes
-deposit myelin within the CNS
Microglia
-remove debris in the CNS
Ependymal Cells
-line the cerebrospinal fluid (CSF) filled cavities of the CNS
Schwann cells
- also called neurolemmocytes
- glial cells that wrap around the cover axons in the PNS
- Form and maintain the myelin sheath
- myelinated: myelin layer is tightly wrapped many times around the axon, forming nodes of ranvier
- increases conduction velocity
Synapses
- regions between adjacent neurons
- presynaptic (toward) and postsynaptic (away)
- Impulses are transmitted by neurotransmitters
- Neurotransmitters are formed in the neuron
Neurotransmitters
-norepinephrine, acetylcholine, dopamine, histamine, and serotonin
Central nervous system (three major divisions of the brain)
- forebrain (two cerebral hemispheres)
- midbrain (corpora quadrigemina, tegmenium, cerebral peduncles)
- hindbrain (cerebellum, pons and medulla)
Brainstem (CNS)
-midbrain, medulla, pons
Reticular formation (CNS)
- network of connected nuclei that regulate vital reflexes, such as cardiovascular and respiratory
- Maintains wakefulness
- together w/ the cerebral cortex is referred to as the reticular-activating system
Forebrain (CNS)
- Telecephalon
- cerebrum (cerebral cortex and basal ganglia)
- Gyri, sulci, fissures
- gray matter and white matter
Frontal lobe
- Prefrontal (goal oriented behavior, short term or recall memory)
- Premotor (motor movement, basal ganglia)
- primary motor areas
- broca speech area
CNS lobes
- parietal lobe (somatic sensory input)
- occipital lobe
- temporal lobe (primary auditory cortex, wernicke area, long term)
Other areas of the CNS
- Corpus callosum
- limbic system
- diencephalon
Limbic system
-primitive behavioral responses, visceral reactions to emotions, motivation, mood, feeding behaviors, biologic rhythms and sense of smell
Diencephalon
- epithalamus
- thalamus
- hypothalamus
- subthalamums
Sections of spinal cord
- cervical-8
- thoracic-12
- lumbar-5
- sacral-5
- coccygeal-1
Protective structures: meninges
- protective membrane that surround the brain and spinal cord
- dura mater
- periosteum
- pia mater
- arachnoid
Protective structures: spaces: Subdural
-located between the dura and arachnoid space
subarachnoid space
-contains CSF and is located between the arachnoid space and pia mater
Epidural
-located between the dura mater and skull
CSF and the Ventricular system
- clear, colorless fluid like blood plasma and interstitial fluid
- circulates between 125-150mL in the ventricles
- reabsorbed through the arachnoid villi
- exerts pressure w/in the brain and spinal cord
- produced by the choroid plexuses in the lateral, third, and fourth ventricle
Vertebral column
-contains 33 vertebrae (7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral, and 4 fused coccygeal)
Blood supply to the brain
- receives 800-1000mL/min
- CO2 is the primary regulator for CNS blood flow
- internal corotid and vertebral arteries
- Blood brain barrier
- arterial circle (circle of willis)
Blood supply to the spinal cord
- vertebral arteries
- -anterior spinal arteries
- -posterior spinal arteries
- -branch off the aorta artery
Autonomic Nervous System
- located in both the CNS and PNS
- coordinate and maintains a steady-state among the visceral (internal organs)
- neurons
- -preganglionic (myelinated)
- -postganglonic (unmyelinated)
- Two divisions
- sympathetic and parasympathetic
sympathetic nervous system
-releases epinepherine and norepinephrine
Adrenergic receptors: a-adrenergic receptors
- A1: adrenergic activity
- A2: adrenergic activity
A1 Adrenergic activity
- mostly associated w/ excitation or stimulation
- Most common
A2 adrenergic activity
-associated w/ relaxation or inhibition
B1 adrenergic activity
-increases heart rate and contractility causes the release of renin from the kidney
B2 adrenergic activity
facilitates all the rest of the b-adrenergic receptors
B3 adrenergic actitivty
-mediates lipolysis and thermogenesis; is upregulated in cardiovascular disease
