 Two divisions:  Central nervous system (CNS)- act as a coordinating centre (brain & spinal cord)  Peripheral nervous system (PNS)- effectors, carry information to and from the CNS.  Further divided into  Somatic – control skeletal muscle, bones & skin  Autonomic – control internal organs of body  Sympathetic  Parasympathetic

 Two different types of cells  Glial (neurological cells; non-conducting, offer structural support and metabolism of nerve cells)  Neurons (functional units of nervous system)  Three groups  Sensory Neurons  Interneurons  Motor Neurons 

 Sensory Neurons  Sense and relay information from environment to CNS  Located in clusters called ganglia  Interneurons  Link neurons within body  Integrate and interpret sensory information and connect neurons to outgoing motor neurons  Motor Neurons  Relay information to effectors (muscles, organs, glands; effectors as they produce responses)

 Messages move from dendrite, through the nerve cell body, to the axon  Axons are covered with a myelin sheath (insulation), made by Schwann cells which prevent loss of charged ions from nerve cells  Areas between sections of myelin are called nodes of Ranvier; nerve impulses jump from one node to another, speeding up messages

 All nerve fibres found within peripheral nervous system contain a thin membrane called neurilemma which surrounds axon  Neurilemma promotes regeneration of damaged axons  Not all nerve cells contain neurilemma and a myelin sheath  Nerves containing mylenated fibres and neurilemma called white matter due to whitish appearance  Grey matter lack myelin sheath and neurilemma and do not regenerate after injury

 The simplest neural circuit is the reflex arc. Reflexes are involuntary. No brain coordination is used. 5 essential components:  Receptor  Sensory neuron  Interneuron (in spinal cord)  Motor neuron  Effector



 Reflex activity  Summary sheet on page 417  Q 1-6, Page 417

 The Electrocardiogram (ECG) is used to diagnose heart problems.  The Electroencephalograph (EEG) is used to measure brain-wave activity  Action Potential – the voltage difference across a nerve cell membrane when the nerve is excited  Resting Potential – voltage difference across a nerve cell membrane during the resting stage (usually negative)  Unlike most cells, neurons have a rich supply of positive and negative ions inside and outside the cell

 The electrochemical event is caused by unequal concentration of positive ions across the nerve cell membrane  Highly concentrated potassium ions inside nerve cells have tendency to diffuse outside the nerve cells  Highly concentrated sodium ions outside the nerve cell tend to diffuse into the nerve cell  As potassium diffuses out of the neuron, sodium diffuses into the neuron  Positively charged ions move both into and out of the cell  The diffusion is not equal and the resting membrane is about 50 times more permeable to potassium ions than to sodium.

 Depolarization must be completed and the nerve repolarized before the next action potential can be conducted as nerves conducting an impulse cannot be activated until the condition of the resting membrane is restored  This time is called the refractory period (usually 1-10 ms) 

 ION GATES CONTROL THE MOVEMENT OF IONS ACROSS THE CELL MEMBRANE.  The separation of electrical charges by the “polarized membrane” has the ability to do work, expressed in millivolts (mV).  Upon excitation, nerve cell membrane becomes more permeable to Na than K  Na ions rush into cell causing depolarization  Once voltage inside cell is +ve, then Na gates close  The sodium-potassium pump located in cell membrane restores condition of resting membrane by transporting Na+ ions out of the neuron while moving potassium ions inside the neuron in a ration of 3 Na + : 2K + ions  ATP fuels the pump

 A nerve or muscle fibre responds completely or not to a stimulus.  Nerves have a threshold level…minimum level of a stimulus required to produce a response.

 Regions b/w neurons  Neurotransmitters…chemicals released into synapses. (i.e. acetylcholine, dopamine etc.)  Can excite or inhibit a neuron from maintaining an action potential.

 Acetylcholine – make post-synaptic membrane permeable to Na+  Cholinesterase (enzyme)…breaks down Acetylcholine...prevents constant depolarization

 Dopamine is the primary neurotransmitter involved in the reward pathways in the brain. Thus, drugs that increase dopamine signalling may produce euphoric effects.  Many recreational drugs, such as cocaine and amphetamines, alter the functionality of the dopamine transporter (DAT), the protein responsible for removing dopamine from the neural synapse.  These changes can strengthen drug craving and alter cognitive pathways, with drug abuse potentially creating drug addiction and drug dependence.

 concentrated in the anterior portion of most animals  brain is covered by meninges  three-layer protective membrane forms the blood/brain barrier  determines which chemicals will reach the brain  cerebrospinal fluid surrounds brain and spinal cord  acts as a shock absorber and a transportation medium of materials  carries nutrients to brain cells  relays wastes from cells to blood

 carries sensory nerve messages from receptors of brain and relays motor nerve messages to  muscles  organs  glands  interneurons are organized into nerve tracts which connect the spinal cord with the brain  dorsal nerve tract brings sensory info into spinal cord  ventral nerve tract carries motor info from spinal cord to peripheral muscles, organs, and glands

 comprised of three main regions  forebrain  midbrain  Hindbrain  Page 428

 contains paired olfactory lobes  receive info about smells  thalamus (below the cerebrum)  relay, consciousness, pain  hypothalamus (below thalamus) (temperature, water, hunger, thirst, sex drive);  direct connection between hypothalamus and pituitary connects nervous system with endocrine system  cerebrum (2 hemispheres connected by the corpus callosum, surrounded by cerebral cortex and divided into 4 lobes:  frontal- voluntary muscles, walking, speech, personality, intellect  parietal- touch, temperature awareness, emotion, interpreting speech  occipital- vision and interpreting visual information  temporal – vision, hearing, memory, interpretation of sensory information

1koQ&feature=related

 relays information to sensory areas (connective)  temporal- vision and hearing, linked to memory  Associative cortex: conceptualization, planning, contemplation, memory.  Motor cortex: voluntary movement of skeletal muscles.  Sensory cortex: vision, hearing, smell.

 Primitive, controls breathing, heart rate, blood pressure.  Main regions of hindbrain  cerebellum, pons, and medulla oblongata  Cerebellum  located immediately beneath two cerebral hemispheres  largest section of hindbrain  deals with coordination and muscle control.

 Pons acts as a bridge.  Passes information between two regions of cerebellum and between cerebellum and medulla   Medulla oblongata  Acts as connection between peripheral and central nervous system  controls involuntary muscle action  diaphragm, heart rate, blood vessel dilation etc.  also acts as coordinating centre for autonomic nervous system.

 Sympathetic NS – prepares body for stress  Parasympathetic NS – return body to normal  Check out table 1 on Page 435

 Endorphins bond to sites on pain receptor ganglia (Substania Ganglia…SG).  Opiates simulate natural endorphins (p. 437)  Heroin, codeine, morphine etc…must continue to take in order to keep working (addiction!)

 Case Study P 432  Q 1-6 p. 434