The Nervous System Chapter 11

Parts of the Nervous System CNS: brain & spinal cord Receives & processes information, initiates effector responses Central N.S. Brain Spinal cord Peripheral N.S. Motor Sensory Autonomic - parasympathetic - sympathetic Somatic PNS: nerves outside CNS Sensory (body- receptors CNS) Motor (CNS  body- effector cell) Somatic division: controls skeletal muscle Autonomic division: controls cardiac muscles, smooth muscles and glands Parasympathetic (calming) Sympathetic (fight-or-flight)

From Cells to Organ Systems Purpose: transmit, control, maintain, process neuron: nerve cell Sensory: sends info to CNS Motor: carries CNS directions to the body Interneuron: relays messages between sensory and motor neurons glial cell: of fifferent types; supports/protects neurons Some form myelin sheaths- e.g. Schwann cells (PNS); oligodendrocytes (CNS) speeds up transmission, & helps damaged/severed axons regenerate - Q: How does structure go with function?

Myelinated neuron Figure 11.7a

From stimulus to response Sensory neuron Dendrite Receptor Cell body Axon Axon terminals Axon bulb Dendrites Axon hillock Interneuron Brain and spinal cord Motor neuron Skin Muscle Impulse direction Figure 11.2 Stimulus triggers sensory receptor on dendrite of sensory neuron The impulse is sent towards the cell body Axons transmit the signal away from the cell body eventually to interneuron Interneuron “processes” info then sends impulse to a motor neuron Motor neuron transmits to an effector (muscle or gland) Muscle or gland responds

Synapse Is a junction, between neurons or neuron and effector cell Between neurons it consists of: 1.Axon terminal of presynaptic (transmitting) neuron 2.postsynaptic (receiving) neuron 3.The two neurons are separated by a space (synaptic cleft) The nerve impulse triggers the release of neurotransmitters from vesicles in axon teminal Neurotransmitters will lead to initiation of an action potential ( nerve signal in second neuron) Figure 11.8

Central Nervous System; brain and spinal cord Figure 11.13

Outer layer of cerebrum Cerebral cortex Outer layer of cerebrum outer region is grey matter (processing, etc.): contains functional areas White matter Inner region is white matter (receiving/sending signals) Parietal lobe Interprets sensory information from skin Occipital lobe Processes visual information Temporal lobe Interprets auditory information Comprehends language Frontal lobe Initiates motor activity Responsible for speech Conscious thought Figure 11.16b

Central Nervous System Central Nervous system: brain and spinal cord CNS protection Bone: skull and vertebrae Meninges: dura mater, arachnoid, and pia mater Cerebrospinal fluid: protective cushion- produced by capillaries Blood–brain barrier: allows limited material across membrane of capillary cells

The brain processes and acts on information Figure 11.15 FOREBRAIN Cerebrum • Coordinates language • Controls decision making • Produces emotions and conscious thought MIDBRAIN • Relays visual and auditory inputs Corpus callosum • Bridges the two cerebral hemispheres Limbic System; Involved in emotions Thalamus • Receives, processes and transfers motor information/sensations HINDBRAIN Pons • Connects cerebellum, spinal cord with higher brain centers • Medulla oblongata • Has vital centers for breathing, heart rate Cerebellum • Controls basic and skilled movements Coordinates movement Q: Which part of the brain classifies humans as “intelligent” beings?

Peripheral Nervous System Transmits information between tissues and CNS Mediated via nerves (collection of neurons) Nerve function depends on its origin and destination Two types of peripheral nerves 12 cranial nerves: connects directly to the brain 31 spinal nerves: connects to the spinal cord Sensory neurons enter spinal cord Motor neurons exits spinal cord

Peripheral Nervous System PNS Somatic division controls skeletal muscles controls voluntary movements Includes spinal reflexes Involuntary responses Does not require conscious thought Central N.S. Brain Spinal cord Peripheral N.S. Motor Sensory Autonomic - parasympathetic - sympathetic Somatic -skeletal muscle -spinal reflexes

Peripheral Nervous System PNS Autonomic division: Sympathetic and parasympathetic motor divisions Central N.S. Brain Spinal cord Peripheral N.S. Motor Sensory Autonomic - parasympathetic - sympathetic Somatic -skeletal muscle -spinal reflexes Oppose each other Helps maintain homeostasis Control functions in cardiac muscles, glands, smooth muscles, etc. Sympathetic stimulates/arouse Parasympathetic relaxes

Sympathetic and parasympathetic motor divisions