Bio11: The Nervous System. Body control systems. The human brain. The human brain. The Cerebrum. What parts of your brain are you using right now?

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1 Bio11: The Nervous System Body control systems Nervous system Quick Sends message directly to target organ Endocrine system Sends a hormone as a messenger to the target organ Can target several organs Slower acting Longer lasting response Work together to regulate body activities What parts of your brain are you using right now? Frontal lobe Movement and conscious thought; speech Frontal area Parietal lobe Speech Somatosensory Taste area Reading Each of the Speech four lobes has distinct functions Hearing Hearing and smell Smell M otorcortex to ma So sensory cortex Auditory area Senses; reading Visual area Vision Vision The human brain The brain processes and acts on information It receives information from nerves and the spinal cord integrates it and generates the appropriate response. Temporal lobe Occipital lobe Figure The human brain Cerebrum largest part of the brain Central processing center where learning, remembering and reasoning takes place The cerebral cortex a highly folded layer of tissue that forms the surface of the cerebrum Cerebrum The Cerebrum Right and left cerebral hemispheres Connected by the corpus callosum Are you left-brained or rightbrained? Right = artistry Left = logic Little about life is that clear and distinct. The traits associated with each side of the brain are matters of degree 1

2 The Cerebrum Gray matter makes up the cerebral cortex mainly cell bodies and nonmyelinated (naked) axons and dendrites. White matter Myelinated axons that connect s in different regions of the cerebral cortex White matter: the brain s connections MRI scan The brain: Cerebellum Coordinates basic movements: Maintains posture and balance Essential for motor coordination and precision. Learns and remembers new motor skills (tying a shoe, playing the piano or hitting a baseball) The brain stem Connects the brain to the spinal cord Controls basic body functions: Breathing Heart rate Temperature control Brain stem The Central Nervous System The central nervous system (CNS) brain spinal cord What protects the CNS? Bone and protective membranes called the meninges a series of 3 coverings between the nervous tissue and bone Spaces filled with cerebrospinal fluid Liquid shock absorber 2

3 Cerebrospinal fluid provides a constant environment CSF protects the brain 1. Cushions the brain 2. Prevents the fragile surface of the brain from striking the skull 3. Maintains consistent chemical environment 4. Allows the brain to be bathed in CSF rather than blood, to avoid bloodborne infection Blood-brain barrier astrocyte Separates the circulating blood from the brain CSF Tight junctions around the capillaries restrict the entry of bacteria and large molecules into the cerebrospinal fluid Protects the brain from bacterial and viral infections Glucose is actively transported across the barrier Spinal cord relays information Neurons are unique cells Superhighway for nerve impulses traveling between the brain and rest of body Vertebra protect the spinal cord nerves Direction of Movement Can be many feet in length! Conduct electrical signals Dendrites, Cell Body, Axon direction Structure of a Dendrites Cell body Direction of electrical signal: Dendrite cell body axon direction Dendrites Cell body An axon ends in a cluster of branches, each with a bulb-like synaptic terminal that relays signals to Another A muscle Axon Supporting cell pathway terminals Axon Supporting cell pathway terminals Nucleus Nucleus Myelin sheath Forms insulating material around an axon Increases the speed of the electrical signal Myelin sheath Figure

4 Types of s Bring messages into SENSORY INPUT brain/spinal cord Types of s SENSORY INPUT Sensory receptor Sensory INTEGRATION Sensory receptor Sensory INTEGRATION MOTOR OUTPUT Inter MOTOR OUTPUT Inter Effector cells Motor system (PNS) Brain and spinal cord Central nervous system (CNS) Effector cells Motor system (PNS) Transfer Brain and spinal cord messages within brain/spinal Central nervous cord system (CNS) Types of s Sensory receptor SENSORY INPUT Sensory MOTOR OUTPUT INTEGRATION Inter Nerves Cables or bundles of axons Extend from the CNS to various parts of the body. Effector cells Motor system (PNS) Take messages from brain/spinal Brain and spinal cord cord to muscles or Central nervous glands system (CNS) The other brain cells (Neurons are not alone) Myelin sheath Neuron Neurons carry electrical signals 100 billion in brain Glia Trillions of support cells Several different types of glia cells help optimize brain function Insulates axons Covering formed by a type of glia called Schwann cells Cells wrap themselves around the axon several times 4

5 What happens if the myelin sheath is damaged? The nervous system has two parts Nerves no longer conduct impulses normally Multiple sclerosis Inflammatory disease that destroys the myelin sheath MS short circuits the nervous system Central Nervous System (CNS) The brain Spinal cord system All nervous tissue outside the CNS Peripheral Nervous System: sensory and motor nerves Sensory nerves bring info from the body to the CNS Information is integrated by inters in brain and spinal cord Response PNS: motor nerves Other nerves serve muscles and glands But not skeletal muscle Controls automatic functions of the body s internal organs Involuntary Autonomic Nervous System Peripheral Nervous System Neurons work by carrying electrical signals Voluntary Carries signals to and from skeletal muscles Involuntary Fight or flight Rest and digest Controls smooth and cardiac muscles, organs and glands Neurons are specialized for carrying electrical signals from one part of the body to another dendrites axon cell body 5

6 The electrical signals are called action potentials An action potential is a brief change in electrical charge at a membrane When a fires, the charge across the s membrane suddenly reverses polarity Action potentials are all or nothing events dendrites axon cell body What happens when a fires? Outside Cell Inside Cell At rest, the Na+ channels are closed. Inside of cell has negative charge When the fires, the Na+ channels open Action potentials spread down the axon Electrical currents involve movement of charged (+ or -) particles Analogy: Power Plant Creates Charge Power Lines Move that Charge (electrical current) To Your House is propagated down the axon like an electrical current down a wire Particles don t move much, they hand their charge off to the next particle How is the action potential passed to the next cell? What happens at the Synapse? Electrical Chemical Electrical Electrical signals can t cross the gap between two s or synapse The signal is transmitted by chemicals called neurotransmitters Stored in vesicles at the end of the axon Bind to receptors on the next cell s 6

7 terminal of sending s Dendrite of receiving SYNAPSE Sending Action potential arrives. Vesicles terminal What happens after the action potential is passed to the next? Receptor Ions Vesicle fuses with plasma membrane. More than 100 small molecules Either excite or inhibit the receiving Most widely studied Acetylcholine (ACh), norepinephrine (NE), dopamine, serotonin, and GABA is released into synaptic cleft. cleft Receiving Ion channels molecules binds to receptor. Ion channel opens and triggers or inhibits a new action potential. Ion channel closes. is broken down and released. Dendrites Myelin sheath Receiving cell body Axon terminals Neurons integrate many signals Neurons and how they work 4:43 SEM A may receive input from hundreds of other s via thousands of synaptic terminals Recap: How s work How do motor nerves control muscle contraction? Motor s carry nerve impulse to a muscle fiber ACh is released, diffuses across the synapse and binds to receptors on muscle cell Muscle fiber contracts 7