Nervous System C H A P T E R 2
Input Output
Neuron 3 Nerve cell Allows information to travel throughout the body to various destinations
Receptive Segment Cell Body Dendrites: receive message Myelin sheath Conductive Segment Axon: transmits message to terminal ending Transmissive Segment neuron 4 Motor end plate Terminal ending on muscle: sends off message to adjacent
Skipping of the impulse allowing faster conduction Myelin sheath: fatty covering or insulator
Types of Neurons Sensory neurons Carry signals to the spinal cord & brain Interneurons Originate and terminate in CNS Connect afferents and efferents in CNS Process incoming signals Pass response impulse on to motor neurons Motor neurons Carry signals from the spinal cord & brain
Types of Neurons cont. 7 Sport Books Publisher
Receptive The Neuron s Function 8 Receptive segment (dendrites) Receives continuous synaptic input (chemical) from other neurons Conductive Conductive segment (axon) Conduction of neural information in the form of nerve impulse (electrical) Transmissive segment (axon terminals) Converts electrical nerve impulse to chemical form (neurotransmitter) and sends it off to dendrites Transmissive
The Nervous system has three major functions: Sensory monitors environment through presence of receptors Integration interpretation of sensory information (information processing) Motor response to information processed through stimulation of effectors
CNS Brain & Spinal Cord Control center PNS Connects CNS with the rest of the body 10
Nervous System Divisions CNS Nervous System Sensory/Afferent PNS Somatic Motor/Efferent Autonomic
Peripheral Nervous System
Peripheral Nervous System 12 pairs of cranial nerves 31 pairs of spinal nerves 8 pairs of cervical nerves 12 pairs of thoracic nerves 5 pairs of lumbar nerves 5 pairs of sacral nerves 1 pair of coccygeal nerves
Spinal Nerve Attachments
Spinal Nerve Attachments (Cont)
CNS: Spinal Cord Consists of neurons through the holes in the vertebrae Holes form a continuous canal Protected by vertebrae, ligaments & cerebrospinal fluid that fills the canal Cord connects to the brain at the brainstem through the foramen magnum
Functions of Spinal Cord 1. Intermediate nerve center between spinal nerves & brain Interneurons integrate messages from various sensory impulses Interneurons can add commands to the msg from the brain
Functions of Spinal Cord (Cont) 2. Major center for reflexes Interneurons can match incoming sensory impulses directly with motor commands without brain intervention
Structure of Spinal Cord Grey Matter White Matter Interneurons, sensory & motor nerve fibers Grey colour: cell bodies of interneurons and moter neurons Bundles of axons White colour: myelin sheaths Dorsal (posterior) Ventral (anterior)
White Matter of Spinal Cord Ascending fibers: sensory information from sensory neurons of body up to brain Descending fibers: motor instructions from brain to spinal cord
Descending Fibers: Voluntary Movements Pyramidal tract Function: Transmit voluntary movement Originates: Motor Cortex and travels through pyramids of medulla Fast tract Extrapyramidal tract Function: Transmit postural adjustments & learned reflexes Travels outside pyramids of medulla Slower pathway: more interneurons: add fine details
CNS: The Brain Primarily composed of interneurons Primary functions parallel the 3 types of neurons: Sensory function Association function Motor function
Regions of the Brain Cerebrum Diencephalon Brain stem Cerebellum
Brainstem Medulla Pons Midbrain Reticular Formation
Medulla Controls breathing, talking, swallowing, maintenance of BP L&R sides= pyramids At medulla nerve fibers cross the body before entering the spinal cord
Pons Links higher brain centers to cerebellum Relay point between brain & spinal cord Influence breathing
Midbrain Smallest division of brainstem Neck & head reflexes Elementary forms of seeing & hearing
Reticular Formation Formation Located in center of brainstem Net-like neural network Alerts the higher brain centers On incoming info Maintains consciousness and alertness
Diencephalon Thalamus Hypothalamus
Relay station between higher & lower centers Thalamus Integrate info gathered from all senses
Regulatory center for activities of the autonomic system Hypothalamus Command center for complex mood & anger, aggression, fear, pleasure, thirst, hunger, sexual behaviour...
Cerebellum General control & coordination center for movement Monitor balance, posture & joint movements Memory capacity for well learned skills
Cerebrum: Cortex Lobes Frontal Lobe Premotor Cortex Motor Cortex Parietal Lobe Sensory Cortex Sensory Association Cortex Temporal Lobe Auditory cortex Auditory association cortex Occipital Lobe Visual cortex Visual association cortex
Touch Proprioception Sensory Cortex
Sensory Association Cortex Receive info from sensory cortex, visual association cortex & auditory association cortex Integrates info and interprets its meaning by comparing it to your past experiences
Visual Cortex
Visual Association Cortex Stores visual memory and permits perception of sight
Auditory Cortex
Auditory Association Area Stores auditory memory and permits perception of sounds
Pre-Motor Cortex Interpret Meaning of Situation Decide whether to take action or not Design plan of action
Motor Cortex Receives action plan from pre-motor cortex Generate commands for muscle activity