GREEN WHITE PURPLE BLUE RED GREEN PINK ORANGE
GREEN WHITE PURPLE BLUE RED GREEN PINK ORANGE BLUE PURPLE YELLOW GREY RED GREEN ORANGE BLACK BLUE RED WHITE YELLOW PINK
GREEN WHITE PURPLE BLUE RED GREEN PINK ORANGE BLUE PURPLE YELLOW GREY RED GREEN ORANGE BLACK BLUE RED WHITE YELLOW PINK
Which circle is not round? They all are
The Nervous System
Two Divisions of the Nervous System: • Central nervous system (CNS) = the brain and spinal cord • Function: controls behavior • Peripheral nervous system (PNS) = a vast network of nerves that conduct impulses between the CNS and the receptors and effectors of the body (via sensory & motor neurons) • Function: responds to the world around you
Stimulus, Receptor, Impulse, Effector • stimulus = something that causes a receptor to trigger impulses in a nerve pathway • receptor = specialized sensing cells that respond to a particular type of stimulus • impulse = message carried by the nerve cells • effector = a muscle or gland that responds to a particular stimulus
The Neuron – aka Nerve Cell Types of Neurons: • sensory neuron = carries impulses from receptors → spinal cord and brain • interneuron = relay impulses from each neuron in brain and spinal column • motor neuron = carries responses from spinal cord/brain → effectors (muscles) « Note: Nerves are bundles of axons or dendrites that are bound together by connective tissues
Organization of the Nervous System
Types of Neurons
Parts of a Neuron: • Dendrites = pick up impulses (from receptors or other neurons) → conducts impulse to cell body • Cell Body = integrates signal, coordinates metabolic activities • Axon = carries impulse away to other neurons/cells • Note: The direction of an impulse always travels from the dendrites → axons
• Myelin Sheath = white, fatty, protein that insulates the axon and prevents the loss of chemical ions (necessary for transmission of impulse) - forms when Schwann cells wrap themselves around an axon • Nodes of Ranvier = gaps on myelinated axons (not covered by the sheath)
Myelin Sheath
• Synaptic terminals = A bulb at the end of an axon in which neurotransmitter molecules are stored and released – Used to transmit signals to other neurons • Note: § there is no contact b/w two neurons § no electrical impulse can pass through them § there is a microscopic space b/w neurons → synapse § there are chemicals (neurotransmitters) that are used to signal the next neuron «Note: enzymes will stop the transmission of the signal
Synapse Structure
Nerve Impulse • When a nerve cell is at rest (not stimulated) → polarized (negative charges inside and positive charges outside the neuron) - allows potassium/sodium ions to move freely across membrane • Depolarized region = when a stimulus passes through the neuron changing the polarity (negative charges on the outside and positive charges on the inside) • Repolarization = restores resting position (negative charges inside/positive outside)
K+ Na+ + - - + + + - - - + + + - - + + + Depolarized Direction of Impulse Polarized = not stimulated (@rest) + + + + - - - - + + + + Repolarization = restores resting potential
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Human Reflexes and Reaction Time The reflex arc • consists of: receptor, sensory neuron, interneuron, motor neuron, effector • a typical reflex arc is the response to pain • it involves only 3 neurons • by-passes the brain
The Nervous System Structure and function of the CNS • the CNS is made of the brain and spinal cord • both are protected by bone (skull and spinal column) • both are protected by 3 tough membranes called the meninges • cerebrospinal fluid (CSF) fills the space between the inner and middle membrane and cushions both the brain and spinal cord
• concussions occur when the brain is severely shaken, causing contact with the skull • 4 spaces in the brain contain the CSF and are called ventricles • ventricles connect with the spaces between the meninges and with the central canal of the spinal cord
Anatomy of the Brain • is the major user of glucose in the body • major parts are the cerebrum, cerebellum, medulla oblongata • other parts are thalamus, hypothalamus, and pons • the forebrain =the cerebrum, thalamus, and hypothalamus • the midbrain = a small area at the top of the medulla oblongata • the hindbrain = the name for the brainstem and the cerebellum
• the brainstem = a name given to the pons, medulla oblongata, and the midbrain Cerebrum • largest part of the human brain • divided in 2 hemispheres (right/left) • a deep groove or fissure divides the 2 hemispheres • a bridge-like connection of nerve fibres between the 2 hemispheres that connects to the rest of the NS is called the corpus callosum
• the two hemispheres do not function equally – one side may be more mathematical, the other may be artistic and musical • the left cerebral hemisphere controls the right side of the body, the right hemisphere controls the left side of the body Functions of the Cerebrum • controls higher processes and senses (speech, reasoning, memory, smell, touch, taste, hearing)
Cerebellum • below the rear part of the cerebrum (back of brain) • Also has 2 hemispheres, white and grey matter Functions of the Cerebellum • coordinates motor movement • staggering and loss of coordination results from impairment of cerebral function (drinking alcohol)
Medulla Oblongata • lowest part of the brain • connected to the spinal cord Functions of the Medulla Oblongata • controls involuntary movement (heartbeat, breathing, blood pressure, yawning, etc)
The Spinal Cord • extends from the opening at the base of the skull, through the vertebral canal, to the lower back • conducts messages between the brain and peripheral nerves (sensory and motor) • controls reflex actions that do not require supervision by higher centers in the brain (the reflex arc)
Somatic and Autonomic Nervous Systems Somatic nervous system • contains both sensory and motor neurons that connect the central nervous system to skeletal muscles, the skin, and the sense organs • is responsible for body movements over which the individual has conscious awareness or voluntary control
Autonomic nervous system • made up of motor fibres from the brain and spinal cord that serve the internal organs of the body • usually has no voluntary control • controls functions like rate of heartbeat, blood flow through arteries, breathing movements, movements of the digestive system, and secretions of certain glands • is made up of 2 systems: – Parasympathetic – Sympathetic «these work in opposite ways to counteract each other
• The parasympathetic system is responsible for ‘rest and digest’ activities, and the sympathetic is responsible for ‘fight or flight’ responses • parasympathetic functions to return to normal operations of the body that were shut down or slowed down by the sympathetic system in an emergency or stressful situation
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