The Nervous System Unit K

Central Nervous System Communication and coordination system of the body Seat of intellect and reasoning. Consists of the brain, spinal cord, and nerves.

NEURON

NEURON

Neuron -Transmits a message from one cell to another -Nerve cell -Transmits a message from one cell to another -Has a nucleus, cytoplasm, and cell membrane Dendrites Nerve cell processes that carry impulse to cell body…may be one or more

Neuron Myelin Sheath Axon Myelin is a fatty substance that protects axon speeds transmission along axon - Called neurilemma Axon -Carries impulses away from the cell body -Only one on a neuron

NERVE IMPULSE A STIMULUS creates an IMPULSE. Impulse to dendrite to axon to neurotransmitter to synapse.

SYNAPSE A space between neurons, messages go from one cell to another.

SENSORY NEURONS (AFFERENT) Emerge from the skin or sense organs. Carry impulses to spinal cord and brain.

MOTOR NEURONS (EFFERENT) Carry messages from brain and spinal cord to muscles and glands.

ASSOCIATIVE NEURONS (INTERNEURONS) Carry impulses from sensory neurons to motor neurons.

NEUROGLIA Cells that insulate, support and protect the neurons, nerve glue.

CENTRAL NERVOUS SYSTEM Divisions of the Nervous System CENTRAL NERVOUS SYSTEM The brain and spinal cord

The Brain 3lb mass of soft nervous tissue 100 billion neurons Protected by skull, 3 membranes called meninges, and cerebrospinal fluid (shock absorber) Cerebrum

BRAIN Adequate blood supply is needed, brain tissue will die in 4-8 mins without O2 Divided into 4 major parts: cerebrum, diencephalon (near midbrain), cerebellum, brain stem

Coverings of the Brain (MENINGES) Meninges surrounds the brain and spinal cord

BRAIN DURA MATER- outer brain covering, lines inside of skull, tough, fluid-containing - dense fibrous connective tissue Layers = dura mater, subdural, arachnoid, subarachnoid, pia mater

Coverings cont’d Subdural space is between the dura and arachnoid space Next layer is the Arachnoid layer - middle layer – resembles fine cob web

SUBARACHNOID SPACE- between arachnoid and pia mater, filled with CEREBROSPINAL FLUID which acts as a liquid shock absorber and as a source of nutrients for the brain

Coverings cont’d PIA MATER innermost layer of the meninges covers the brain’s surface, comprised of blood vessels held together by connective tissue

Meninges

Meninges

Meningeal Layers https://www.youtube.com/watch?v=1liTxUxT9xQ https://www.youtube.com/watch?v=ak1FWodg5Nw

Ventricles of the Brain Brain contains four cavities filled with cerebrospinal fluid called CEREBRAL VENTRICLES.

Ventricles

Ventricles of the Brain (cont.) CHOROID PLEXUS- network of blood vessels lining the ventricles which helps in the formation of cerebrospinal fluid. CEREBROSPINAL FLUID Forms inside ventricles of the brain. Serves as a liquid shock absorber

Choroid Plexus

BLOOD-BRAIN BARRIER- choroid plexus capillaries prevent substances (like drugs) from penetrating brain tissue – this makes infections, like meningitis, difficult to cure. LUMBAR PUNCTURE- removal of CSF from spinal canal, needle puncture between 3rd and 4th lumbar vertebrae.

Blood Brain Barrier

Lumbar Puncture

CEREBRUM Largest part of the brain Divided into R and L hemispheres by deep groove The convolutions of the brain increase the surface area, or cortex, and allow more capacity for the neurons that store and process information. Each convolution contains two folds called gyri and a groove between folds called a sulcus

SULCI - fissure or grooves separating cerebral convolutions

CEREBRUM IS… Divided into four lobes – FRONTAL (voluntary muscle movement), PARIETAL, OCCIPITAL and TEMPORAL

Frontal Lobe Emotions, problem solving, memory, language, judgment, decision making, normal speech

Parietal Lobe Sensation and perception

Occipital Lobe Visual processing center

Temporal Lobe Auditory perception

CEREBRAL FUNCTION Conscious thought, judgment, memory, reasoning, and will power. - responsible for maintaining consciousness, decision making, recalling information and normal speech These people were not using their cerebrum.

Limbic System complex set of structures that lies on both sides of the thalamus, just under the cerebrum Instinct and mood

Located between cerebrum and midbrain DIENCEPHALON Located between cerebrum and midbrain Composed of THALAMUS and HYPOTHALAMUS

Vital functions of the hypothalamus: 1. Autonomic nervous control 2. Temperature control 3. Appetite control 4. Emotional state 5. Sleep control

CEREBELLUM 2nd largest part of brain Composed of two hemispheres below the cerebrum Controls all body functions related to skeletal muscles, including: Balance, walking Muscle tone Coordination of muscle movements

Controls all body functions related to skeletal muscles, including: Balance, walking Muscle tone Coordination of muscle movements

BRAIN STEM Made up of PONS, MEDULLA and MIDBRAIN Pons – in front of cerebellum, between midbrain and medulla – contains center that controls respiration Midbrain – controls vision and hearing Medulla oblongata – bulb-shaped structure between pons and spinal cord, inside the cranium above foramen magnum (opening in vertebral column) - Responsible for: 1. Heart rate 2. Blood pressure Click for picture…

Brain/BrainStem https://www.youtube.com/watch?v=YDA7gGjpPWM

SPINAL CORD Begins at foramen magnum and continues down to 2nd lumbar vertebrae White and soft, in spinal canal Surrounded by cerebrospinal fluid FUNCTIONS AS: Reflex center Conduction pathway to and from the brain Injury to spinal cord = difficulty with movement (paraplegia – paralysis of legs) and problems breathing

Peripheral Nervous System All of the nerves outside the central nervous system NERVES Contains sensory and motor nerves (afferent and efferent)

Peripheral Nervous System (PNS) Cranial nerves and spinal nerves are part of the PNS

Cranial Nerves 12 pairs Begin in the brain Designated by number and name

Mnemonic for the 12 cranial nerves Oh To Touch And Feel Vestibularcochlear Good Velvet A H Mnemonic for the 12 cranial nerves

SPINAL NERVES Originate at spinal cord and go through openings in vertebrae 31 pairs of spinal nerves All are mixed (afferent and motor) nerves Named in relation to their location on the spinal cord

AUTONOMIC NERVOUS SYSTEM Regulates activities of visceral organs (i.e. beating of heart) Not subject to conscious control SYMPATHETIC NERVOUS SYSTEM- the “fight or flight” system- when the body perceives danger, SNS sends message to adrenal medulla (above kidney) to secrete adrenaline - heartbeat increases, dry mouth resp rate increases, etc

Parasympathetic Nervous system counters SNS – decreases heart rate, decreases respiratory rate, etc REFLEX Unconscious and involuntary In a simple reflex, only a sensory nerve and motor nerve involved – example “knee-jerk” reflex

Autonomic Nervous System Peripheral nerves and ganglia Supplies heart muscle, smoother muscle and secretory glands Involuntary i.e. automatic responses to injury like shock and increased heart rate

Disorders of the Nervous System MENINGITIS Inflammation of the lining of the brain and spinal cord May be bacterial or viral Symptoms- headache, fever and stiff neck, nausea and vomiting In severe form, may lead to paralysis, coma and death If bacterial, may be treated with antibiotics Dx by removing csf with a needle = lumbar puncture

EPILEPSY Seizure disorder of the brain, characterized by recurring and excessive discharge from neurons Seizures believed to be result of spontaneous, uncontrolled electrical activity of neurons Cause – Uncertain Victim may have hallucinations and seizures Grand mal – severe, convulsive seizure Petit mal - milder

Epilepsy Seizure disorder of the brain Recurring and excessive discharge from neurons Result of spontaneous, uncontrolled cycles of electrical activity in neurons Hallucinations, seizure, loss of consciousness Grand mal-more severe Petit mal-milder, victim may be staring

Epilepsy

Epilepsy https://www.youtube.com/watch?v=CDccChHrgRA

CEREBRAL PALSY Disturbance in voluntary muscular action due to brain damage. May be due to birth injury or abnormal brain development Spastic Quadriplegia- spastic paralysis in all four limbs. Sx- head rolling, grimacing, difficult speech and swallowing No impairments of intellect.

CP https://www.youtube.com/watch?v=MDO6bijBRHs https://www.youtube.com/watch?v=buRLc2eWGPQ https://www.youtube.com/watch?v=dBccclL0VHg

POLIOMYELITIS DEMENTIA Viral disease of nerve pathways of spinal cord- causing progressive muscle weakness leading to paralysis Almost eradicated in USA (vaccine) DEMENTIA Loss of 2 areas of complex behavior, such as languages, memory, visual and spatial abilities, or judgment Interferes with person’s daily life.

Polio https://www.youtube.com/watch?v=lDMoBcZG72E

HYDROCEPHALUS Increased volume of cerebrospinal fluid within ventricles of the brain. Usually, blockage in 3rd and 4th ventricle Enlargement of the head, usually noticed at birth. Bypass or shunt performed to relieve pressure.

Hydrocephalus

Hydrocephalus https://www.youtube.com/watch?v=QSPTTdu63TQ

Abnormal fibers build up creating tangles ALZHEIMER’S DISEASE Progressive disease that begins with problems remembering – characterized by early senility, confusion, and loss of recognition of persons Nerve endings in cortex of brain degenerate and block signals that pass between nerve cells Abnormal fibers build up creating tangles

Cause – Unknown 1st stage (2-4 yrs) involves confusion, short-term memory loss, anxiety, poor judgment 2nd stage (2-10 yrs) increase in memory loss, logic problems, and loss of social skills 3rd stage (1-3 yrs) inability to recognize oneself, weight loss, seizures, mood swings and aphasia

Alzheimer’s Disease https://www.youtube.com/watch?v=P4UMfBK1UQk

PARKINSON’S DISEASE Symps - tremors, shuffling gait, pill-rolling, and muscular rigidity. Decrease in neurotransmitter dopamine RX- L-dopa and other drugs to treat symptoms.

Parkinson’s https://www.youtube.com/watch?v=hu4eTijdIv0

Chronic inflammatory disease of CNS - autoimmune MULTIPLE SCLEROSIS (MS) Chronic inflammatory disease of CNS - autoimmune Immune cells attack myelin sheath of axon-myelin sheath destroyed, leaving scar tissue on nerve cells…transmission of nerve impulses blocked.

Cause- UNKNOWN Sx- weakness of extremities, numbness, double vision, nystagmus, speech problems, loss of coordination, possible paralysis. Typically strikes young adults age 20-40, mostly women Rx- Avonex- slows progression

Multiple Sclerosis https://www.youtube.com/watch?v=h19muxVqiOs

Spinal Cord Injury May be injured at any level Site of injury, type of trauma, and the degree of injury determine whether paralysis will occur and whether it’s temporary or permanent

Spinal Cord Injury C1-C3: highest level of spine; injury there is usually fatal. C1-C4: quadriplegia or loss of feeling and movement in trunk and all four extremities with accompanying loss of bowel, bladder, and sexual function C5-C7: varying degrees of paralysis of arms and shoulders

Spinal Cord Injury T1-T12 and L1-L5: paraplegia or loss of movement and feeling in trunk and both legs; loss of bladder, bowel, and sexual function are common. Treatment: suspected spinal cord patients need IMMEDIATE attention; NEVER MOVE A VICTIM UNLESS SURROUNDINGS ARE LIFE THREATENING

Spinal Cord Treatment: realignment, stabilization and release of pressure on spine; prevention of further injury

Spinal cord Injury-MR before https://www.youtube.com/watch?v=tQ8k0QnhUWg https://www.youtube.com/watch?v=bpsvYLpa9vQ

Spinal cord Injury-MR after https://www.youtube.com/watch?v=NYnf-bMZQoE https://www.youtube.com/watch?v=xPpQIgo41y8

West Nile Virus Mosquito-borne virus Spread to humans by bites of mosquitoes No symptoms or mild flu like symptoms In the elderly, virus may cause encephalitis or meningitis