Functions of the nervous system
Receive sensory input from internal and external environments: Ex. pressure, taste, sound, light, blood pH, hormone levels- converted to a signal and sent to the brain or spinal cord Integrate the input: In the sensory centers of the brain or spinal cord, the barrage of input is integrated and a response is generated Respond to stimuli: The response, a motor output, is a signal transmitted to organs that then can convert the signal into some form of action Ex. movement, changes in heart rate, release of hormones
Central nervous system
brain and spinal cord
Peripheral nervous system
nerves that connect the brain and spinal cord to the rest of the body, carries nerve impulses sent between CNS and the rest of the body. Ex. sensory neurons, motor neurons, somatic nervous system, autonomic nervous system, cranial nerves, spinal nerves
Brain's three major parts
cerebrum, cerebellum, brain stem
Hypothalamus
controls temperature and appetite
Cerebrum
largest part of the brain, contains the parietaI, frontal, temporal, and occipital It is divided into 2 hemispheres by longitudinal fissure Rt. hemisphere is creative side, controlling artistic ability and emotions The left hemisphere contains centers for speech, thinking, voluntary movement, reading, writing, hearing, vision, and motor action Corpus callosum (white matter) connects right and left hemispheres Cerebral surface: covered in ridges (gyri) and grooves (sulci) Outer layer: cerebral cortex (gray matter) Cerebrum divided from cerebellum by transverse fissure
Cerebellum
(little brain) essential for coordination of voluntary movement Maintaining balance Coordination of eye movements Holds more than ½ of neurons of entire body
Brain stem
Relay center connecting cerebellum and cerebrum to spinal cord Performs many autonomic features breathing, heart rate, digestion, sneezing, coughing, swallowing 10 of 12 cranial nerves emerge from brainstem Contains the midbrain, pons, and medulla oblongata
Midbrain
associated with vision, hearing, motor, control, sleep wake cycles, alertness, and T regulation Relays sensory and motor info
Pons
relays sensory and motor info from forebrain to cerebellum, role in sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation and posture
Medulla oblongata
lower half of brain stem Vital functions cardiac, respiratory, vomiting, and vasomotor centers Regulates autonomic, involuntary functions like breathing, heart rate, and blood pressure
Spinal cord
Cable of nerve tissue extends from medulla oblongata to lumbar region of vertebral column Nerve impulses from body and brain run up and down Reflexes Surrounded and protected by vertebrae
Meninges
3 membranes lining skull and vertebral canal enclose the brain and spinal cord- sterile atmosphere Brain/spinal cord surrounded by meninges for protection Act as cushions and shock absorbers Dura mater, Arachnoid mater, Pia mater
Dura mater
thick, outermost layer of the meninges surrounding and protecting the brain and spinal cord
Arachnoid mater
middle layer of the meninges
Pia mater
thin, delicate inner membrane of the meninges
Cerebral spinal fluid
clear liquid that bathes brain/spinal cord Subarachnoid space between arachnoid and pia Contains glucose, protein, H2O Acts as a shock absorber
Cranial nerves
They extend from out the brain 12 pairs- designated by name and number Connect the brain to the head (functionally) Most carry both sensory and motor fibers
Olfactory I
sensory neuron, smell
Optic II
sensory neuron, vision
Oculomotor III
motor neuron, most eye movement
Trochlear IV
motor neuron, moves eye
Trigeminal V
sensory and motor neuron, face sensation, mastication
Abducens VI
motor neuron, abducts the eye
Facial VII
sensory and motor neuron, facial expression, taste
Vestibulocochlear VIII
sensory neuron, hearing, balance
Glossopharyngeal IX
sensory and motor neuron, taste, gag reflex
Vagus X
sensory and motor neuron, gag reflex, parasympathetic innervation
Accessory XI
motor neuron, shoulder shrug
Hypoglossal XII
motor neuron, swallowing, speech
Spinal nerves
31 pairs of peripheral nerves- contain both sensory and motor fibers 8 pairs cervical 12 pairs thoracic 5 lumbar 5 pairs sacral 1 coccygeal
Sensory neurons
Carry nerve impulses from sense organs and receptors to the CNS, also called afferent neurons
Motor neurons
Carry impulses from CNS to the muscles and glands Also called efferent neurons contains somatic and autonomic
Interneurons
conduct impulses from sensory neurons to motor neurons, also called central or connecting neurons
Somatic nervous system
controls skeletal muscle and voluntary movements
Autonomic nervous system
organs, controls smooth and cardiac muscle and several glands, systems are involuntary Ex. heartbeat, breathing contains sympathetic and parasympathetic
Sympathetic
body's accelerator triggered by alarm state, "fight or flight", all voluntary systems (mainly muscles)
Parasympathetic
body's brake triggered by relaxation, organs and systems not under voluntary control, Ex. rest or digest
Neuron
transmitting a message from one cell to the next
Synapse
gap between neurons, a junction where information is transmitted from one neuron to the next.
Dendrite
fibers extending from a neuron cell that conduct impulses toward the cell body
Axon
a fiber extending from a neuron cell that conducts impulses away from the cell. Each nerve cell has only one axon
Myelin sheath
a fatty tissue that wraps the axon to protect it and helps speed up impulses as they travel down the axon
Neurotransmitters
Epinephrine Norepinephrine Acetylcholine- between muscles and nerve cells
Multiple sclerosis
Myelin destroyed, may involve the axon and cell body- conduction slow or impossible Usually involves brain, spinal cord, and optic nerves Symptoms differ depending on where the myelin damage occurs Causes disturbances in vision, balance, speech or movement No cure, medications can slow progression, learn to manage symptoms
Cerebrovascular accident
Stroke Brain tissue dies Symptoms sudden and many are permanent Can be due to bleeding in the brain (hemorrhagic) or disruption of blood flow (ischemic) Sensory, language, motor and/or memory difficulties
Alzheimer's disease
progressive, cause not fully known Begins with difficulty remembering recently learned info (short term memory loss) Believed to be a build up of plaque (destruction of nerve endings in the cortex that block signals between nerve cells), and a defect in the neurotransmitters
Myasthenia gravis
a chronic autoimmune disease that affects the neuromuscular junction and produces serious weakness of voluntary muscles
Traumatic brain injuries
Force applied to the skull, causing damage to the brain tissue Closed-: skull not open Penetrating: skull punctured Concussion: a more mild brain injury Contusion: more serious, characterized by swelling and/or bleeding
Autism
A developmental disorder marked by disabilities in language, social interaction, and the ability to understand another person's state of mind
Meningitis
an infection of the meninges, causing inflammation of the meninges Bacterial: IV antibiotics, if untreated can cause seizures, coma, amputation of limbs, or death Viral: bed rest, fluids, medications to relieve symptoms
Amyotrophic Lateral Sclerosis
Muscle weakness, twitching and cramping, progresses to complete paralysis, difficult speaking and swallowing, diaphragm paralyzed Motor neurons in cerebral cortex, brain stem, and spinal cord self-destruct