The nervous system is made up of: The spinal cord The nerves The senses The brain

The Nervous System

    Complex system in the body made up of many parts Divided into two main systems  the central nervous system (CNS)  the peripheral nervous system (PNS) CNS  consists of the brain and spinal cord Gets info. from the body and sends out instructions PNS  consists of all the nerves and wiring Sends messages from the brain to the rest of the body

Peripheral Nervous System

     A communication system 3 kinds of neurons connect the CNS to the body  Sensory   Motor Interneurons Sensory- sensory receptors to CNS Motor- CNS to muscles Interneurons- Connections within CNS

Peripheral Nervous System

   Unlike other system we have been studying, neurons have a limited ability to repair themselves nerve cells also have a limited ability for repair if damaged due to injury or disease Ex.) Spinal injuries

Neurons

   Cell Body : functional part Dendrites : short extensions that receive signals Axon : long extension that transmits impulses away

Nerve Impulses

 Messages carried throughout the body by nerves  Your funny bone is the only nerve on your arm that is not protected!!! FUNNY HUH?

The Action Potential

 Threshold potential will trigger an action potential or nerve impulse  The action potential is an all-or- none response

Myelinated Neurons

   Myelin sheathing allows neurons to conduct nerve impulses faster than non-myelinated neurons Myelin insulating sheath around the axon is formed by Schwann cells Myelin sheathing has bare patches of axon called nodes of Ranvier

Signals move from neuron to neuron

    A synapse divides 2 neurons The action potential will not move across the synapse At the end of an axon, the arrival of an action potential results in the transfer of info. to another neuron Communication between neurons occurs in one direction only across a synapse  Presynaptic neuron  postsynaptic neuron

Signals move from neuron to neuron cont.

  Communication between neurons occurs in one direction only across a synapse  Presynaptic neuron  neuron postsynaptic Synaptic cleft must be crossed for the presynaptic neuron to cross and bind to the postsynaptic neuron

Neurotransmitters

   This is done through the release of chemicals called neurotransmitters Move by diffusion across the synaptic cleft There are many different neurotransmitters

Neurotransmitters

  Common Neurotransmitters (brain & Autonomic NS):    Acetylcholine (ACh) (muscular junctions, glands, brain & spinal cord) Norepinephrine (NE) (brain regions- emotions, dreaming) Excitatory CNS neurotransmitters:    Dopamine Serotonin Inhibitors

Nerve signals jumping synaptic cleft

The axon of one neuron doesn't touch the dendrites of the next. Nerve signals have to jump across a tiny gap (synaptic cleft). To get across the gap they have to change from electrical signals into chemical signals (neurotransmitters) then back into electrical signals.

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Peripheral Nervous System

Peripheral Nervous System Skeletal (Somatic) Autonomic Sympathetic Parasympathetic

Basic Tasks of the Nervous System

Sensory Input:

Monitor both external and internal environments.

Integration:

Process the information and often integrate it with stored information.

Motor output:

If necessary, signal effector organs to make an appropriate response.

Sensory and Motor Pathways

     SENSORY PATHWAY Signals from external environment, skin, muscles, internal organs etc a sensation arrives in the form of an action potential carries fine touch and pressure sensations Sensations travel to the thalamus and are sorted accordingly

Sensory and Motor Pathways

    MOTOR PATHWAY: Provides voluntary skeletal muscle control A rapid, direct mechanism In response to the sensory pathway, the CNS issues motor commands distributed by the somatic and

autonomic nervous systems

Somatic Nervous System

    Nerves to and from spinal cord Both voluntary and reflex movements Skeletal reflexes Directs contractions of skeletal muscles

Autonomic Nervous System

    Issued outside our conscious awareness

Activities you don’t think about!

Controls involuntary functions  Heartbeat    Blood pressure Respiration digestion Can be influenced by thought and emotion

Autonomic Nervous System



Two divisions:



Sympathetic



Parasympathetic

Sympathetic

CENTRAL NERVOUS SYSTEM Brain Dilates pupil SYMPATHETIC

     “Fight or Flight” response Released adrenaline and noradrenaline Increased heart rate and bp Increased blood flow to skeletal muscles Inhibits digestive functions

Spinal cord Sympathetic ganglia Stimulates salivation Relaxes bronchi Accelerates heartbeat Inhibits activity Stimulates glucose Secretion of adrenaline, nonadrenaline Relaxes bladder Stimulates ejaculation in male Salivary glands Lungs Heart Stomach Pancreas Liver Adrenal gland Kidney

Parasympathetic

   “Rest and digest” system Calms body to conserve and maintain energy Lowers heartbeat, breathing rate and bp

Central Nervous System

   

Spinal Cord

Sends messages to the brain Part of the nervous system that connects the brain to the rest of the body Thickest nerve is 1 inch thick and the thinnest is thinner than a human hair

Spinal Cord

  The spinal cord runs down a tunnel of holes in your backbone or spine The vertebrae are the many bones that protect the nerves in the spinal cord from damage

Central Nervous System

    

Brain

helps to control all of the body systems and organs allows us to think, feel, remember and imagine communicates with the body through the spinal cord and the nerves Tells the body what to do and when to do it

Major divisions of the brain

      The cerebrum The diencephalon The pons---------------- The midbrain----------- The medulla oblongata- The cerebellum

Cerebrum

  Divided into large, paired cerebral

hemispheres

hemispheres are covered by a thick blanket of neural cortex called the cerebral cortex       Thinking sensations intellectual functions memory (storage and retrieval) complex motor pattern speaking

Diencephalon

    A hollow division of the brain that includes the thalamus and hypothalamus Connected to cerebrum Its sides form the thalamus Its floor forms the hypothalamus where a narrow stalk connects it to the pituitary

gland

Diencephalon cont.

   Thalamus – contains relay and processing centers for sensory info.

Hypothalamus – involved with emotions, autonomic function and hormone production Pituitary gland – 1° link between the nervous system and endocrine system

Brain Stem

  Consists of  Midbrain   Pons Medulla Contains important processing centers and relay stations for info. headed to/from cerebrum or cerebellum

Midbrain

    Middle Visual and auditory information Generates involuntary motor responses Maintenance of consciousness

Pons

     Bridge Connects the cerebellum to the brain stem Tracts and relay centers Contains nuclei involved with somatic and visceral motor control Connect to the medulla oblongata

Medulla Oblongata

   Attaches to the spinal cord Relays sensory info. to the thalamus and other brain stem centers Regulation of autonomic functions     Heart rate Blood pressure Respiration Digestive activities

Cerebellum

    Lg. and sm. hemispheres cover most of the brain stem Adjust voluntary and involuntary motor activities based on sensory info. and stored memories of previous movements Controls balance and posture

Brain

     Has 2 hemispheres Left & Right sides are separate Corpus Callosum: major pathway between the two hemispheres Permits data received on one side to processed in both hemispheres Language on left, Math, music on right 

Note* this is never 100%

Brain

 Each hemisphere is divided into 4 lobes  Frontal    Parietal Occipital Temporal

The Brain

Frontal Lobe

     Contains 1° working cortex Working memory prefrontal

Working Memory

No direct sensory input Important planning and sequencing areas Area for speech

Motor Cortex

Phineas Gage

       Railroad worker Iron rod straight through his skull SURVIVED!

Entered cheek bone and excited top of skull Went through frontal lobe Led to important discoveries in neurology b/c his behavior could be studied Changes in personality, work ethic, speech, planning etc.

Parietal Lobe

   Inputs from multiple senses Borders visual & auditory cortex Outputs to frontal lobe  Hand-eye coordination   Eye movements attention

Parietal Lobe

Temporal Lobe

  1° auditory cortex Auditory & Visual patterns     Speech recognition Face recognition Word recognition Memory formation

Auditory Cortex Temporal Lobe

Occipital Lobe

   Input from optic nerve Contains 1° visual cortex

Occipital Lobe

Outputs to parietal

Visual Lobe

and temporal lobes

The Senses

     Sight Taste Touch Hearing Smell  Carry messages about the environment to the central nervous system

Examples of Sense Organs

 Eyes, ears, nose, tongue, and skin  Sense organs gather information from the environment     Light Sound Heat pressure

Seeing - Vision

 Your ability to see  Involves the eye and the brain  The blind spot for the eye is caused by the optic nerve

Sight Receptors

   Photoreceptors – rods and cones of the retina- detect photons basic unit of light Rods provide the CNS with info. on the presence or absence of photons No colors of light, very sensitive, enables us to see in dim rooms

Hearing

 Hearing begins when some of the sound waves go into the ear  When a sound is made, the air around the sound vibrates

Hearing

    Ear captures and transmits info. about movement, gravity and sound Sound converted into action potentials in the cochlea Hair cells are deflected as sound waves move through the cochlea Action potentials are sent to the brain via the auditory nerve

Hearing

     Loud sounds can damage hair cells leading to cell death and deafness Once hair cells have died, they do regenerate External (pinna)- collects/directs sound Middle- collect/amplify sound waves Inner- sensory organs responsible for equilibrium

Touch

     Sense of touch is located on the skin Nerves in the skin allow us to feel texture, pressure, heat, cold and pain Thermoreceptors- temperature receptors Tactile receptors- touch, pressure and vibration Baroreceptors- monitor changes in pressure

Smell

    The nose controls your sense of smell Olfactory receptors aid with smelling *the nose can smell 80 different kinds of smells* Doesn’t come close to comparing with that of other animals

Taste

   Sense of taste comes from the taste buds on your tongue Taste Buds (taste receptors) are the parts on the tongue that allow us to taste there are 4 kinds of taste buds:  Sweet    Sour Bitter salty

12 Cranial Nerves

I - Olfactory II - Optic III - Oculomotor IV - Trochlear V - Trigeminal VI - Abducens VII - Facial VIII - Auditory IX - Glossopharyngeal X - Vagus XI - Accessory XII - Hypoglossal

Cranial Nerves

   

Olfactory nerves(I)–

 Sensory, smell

Optic nerves(II) –

 Sensory, vision

Oculomotor nerves(III) –

 muscles that move the eyeball

Trochlear nerves(IV) –

 smallest cranial nerves  innervate the superior oblique muscles of the eyes

Cranial Nerves Cont.

   

Trigeminal nerves(V) –

  largest cranial nerves, ophthalmic, maxillary and mandibular branches

Abducens nerves(VI) –

 innervate the intrinsic eye muscle (lateral rectus) Facial nerves(VII) – mixed nerves    control muscles of scalp & face provide pressure sensations over face receive taste information from tongue

Vestibulocochlear nerves(VIII) –

  vestibular nerves (monitor balance, position & movement) cochlear nerves (monitor hearing)

Cranial Nerves Cont.

   

Glossopharyngeal nerves(IX) -

  mixed nerves that innervate tongue & pharynx Control swallowing

Vagus nerves (X)–

 mixed nerves, vital to autonomic control of visceral fxn  have a variety of motor components

Accessory nerves(XI) –

  Medullary Branch- innervates swallowing muscles of soft palate & pharynx Spinal Branch- controls muscles in pectoral girdle

Hypoglossal nerves(XII) –

 voluntary control over tongue movements