Regents BiologyAP Biology Nervous System

Regents Biology This science is called Neurobiology Looking at the actual cells - how do they work? Looking at the connections - how and when do they work? Looking at what can change normal cells and connections Looking at diseases that occur in the brain One of the largest areas still unknown The you that is you is because of your neurons connecting!

Regents Biology Fun facts about neurons Most specialized cell in animals Longest cell blue whale neuron meters giraffe axon 5 meters human neuron 1-2 meters Nervous system allows for 1 millisecond response time

Regents Biology The Nervous System A network of billions of nerve cells linked together in a highly organized fashion to form the rapid control center of the body. Functions include: Integrating center for homeostasis, movement, and almost all other body functions. The mysterious source of those traits that we think of as setting humans apart from animals

Regents Biology Basic Functions of the Nervous System 1.Sensation Monitors changes occurring in and outside the body: stimuli 2.Integration The parallel processing and interpretation of sensory information to determine the appropriate response 3.Reaction Motor output. The activation of muscles or glands via the release of neurotransmitters (NTs))

Regents Biology Motor Efferent Division Can be divided further: Somatic nervous system VOLUNTARY (generally) Somatic nerve fibers that conduct impulses from the CNS to skeletal muscles Autonomic nervous system INVOLUNTARY (generally) Conducts impulses from the CNS to smooth muscle, cardiac muscle, and glands.

Regents Biology Autonomic Nervous System Can be divided into: Sympathetic Nervous System “Fight or Flight” Parasympathetic Nervous System “Rest and Digest” These 2 systems are antagonistic. Typically, we balance these 2 to keep ourselves in a state of dynamic balance. We’ll go further into the difference btwn these 2 later!

Regents Biology Nervous Tissue 2 cell types 1.Neurons Functional, signal conducting cells 2.Neuroglia (“glial cells”) Supporting cells 1. 2.

Regents Biology 1.Schwann cells Form myelin sheaths around the larger nerve fibers in the PNS. Vital to neuronal regeneration Neuroglia

Regents Biology Nervous vs. Endocrine System Similarities: They both monitor stimuli and react so as to maintain homeostasis. Differences: The NS is a rapid, fast-acting electrical system whose effects do not always persevere. Stimulus is non specific: cell/tissue contacted will respond. The ES acts slower (via chemical signals called H _ _ _ _ _ _ _) and its actions are usually much longer lasting. Hormones travel through the blood stream and affect target cells only.

Regents Biology Nervous System Central nervous system brain & spinal chord Peripheral nervous system nerves from senses nerves to muscles cerebrum cerebellum spinal cord cervical nerves thoracic nerves lumbar nerves femoral nerve sciatic nerve tibial nerve

Regents Biology Nervous system cells dendrites cell body axon synapse  Neuron  a nerve cell signal direction signal direction

Regents Biology Human Neuron Diagram Dendrite Axon terminals Cell body Axon Myelin sheath Node of Ranvier

Regents Biology Myelination in the CNS Myelination in the PNS

Regents Biology Myelin coating signal direction myelin coating Multiple Sclerosis  immune system (T cells) attacks myelin coating  loss of signal Multiple Sclerosis  immune system (T cells) attacks myelin coating  loss of signal  Axon coated with insulation made of myelin cells  speeds signal  signal hops from node to node  330 mph vs. 11 mph

Regents Biology How are neurons “connected”? Synapses!!

Regents BiologySynapse Junction between nerve cells 1st cell releases chemical to trigger next cell where drugs may affect nervous system synapse

Regents Biology AXON The synapse - where the action happens The next cell’s plasma membrane What is this in the membrane ? Transport protein Close up look at your synapse

Regents Biology How does the Synapse carry the signal? 1.Electrical current travels down the axon 2.Vesicles with chemicals move toward the membrane and merges with the membrane of synaptic bulb- what is that process called? 3.Chemicals are released and diffuse toward the next cell’s plasma membrane 4.The chemicals open up the transport proteins and allow the signal to pass to the next cell - what type of transport is this? k.html

Regents Biology The synapse carries a signal from cell to cell

Regents Biology Resting potential When a neuron is at rest, the inside of the neuron is negative relative to the outside. Although the concentrations of the different ions attempt to balance out on both sides of the membrane, they cannot because the cell membrane allows only some ions to pass through channels (ion channels). There is a charge imbalance. (The resting membrane potential of a neuron is about -70 mV). At rest, there are relatively more sodium ions outside the neuron and more potassium ions inside that neuron.

Regents Biology Occurs when a neuron sends information down an axon, away from the cell body. A stimulus causes the resting potential to move toward 0 mV. When the depolarization reaches about -55 mV (threshold level) a neuron will fire an action potential. If the neuron does not reach threshold level: no action potential will fire. When threshold level is reached, an action potential of a fixed sized will always fire. The size of the action potential is always the same. This is the "ALL OR NONE" principle. Action potential

Regents Biology They have 2 gates. 1 2 Na transport proteins

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Absolute Refractory Period During the time between the opening of the Na + channel activation gate and the opening of the inactivation gate, a Na + channel CANNOT be stimulated. This is the REFRACTORY PERIOD. Thus the action potential is unidirectional.

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Regents Biology How is a toilet like the effect of an action potential on voltage-gated channels? All or none response Threshold stimulus Refractory period Clogs

Regents Biology Toilet handle triggers the flushing. Voltage-gated channels trigger an action potential if the membrane is stimulated with enough voltage (threshold). If pressed hard enough a complete flush will occur but pushing even harder on the handle will not make a bigger flush. This is true for the action potential, hence all-or-none. The flush involves movement of "materials" through the plumbing; the action potential involves movement of Na ions through "plumbing" (voltage-gated channels. The driving force for fluid movement in the toilet is the water pressure from the water. The ‘pressure’ source for Na ion movement is the electrochemical gradient for Na. Finally, the clog: Well, use your imagination, but illegal drugs and toxins can be the “clog” in action potential propagation.

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Types of neurons sensory neuron (from senses) interneuron (brain & spinal chord) motor neuron (to muscle)

Regents Biology Action Potential Conduction If an AP is generated at the axon hillock, it will travel all the way down to the synaptic knob. The manner in which it travels depends on whether the neuron is myelinated or unmyelinated. Unmyelinated neurons undergo the continuous conduction of an AP whereas myelinated neurons undergo saltatory conduction of an AP.

Regents Biology In this situation, the wave of depolarization travels along the axon Analogous to dominoes falling. In unmyelinated axons:

Regents Biology Saltare is a Latin word meaning “to leap.” Recall that the myelin sheath is not completed. There exist myelin free regions along the axon, the nodes of Ranvier. Myelinated axons: Saltatory Conduction

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Rates of AP Conduction 1.Which do you think has a faster rate of AP conduction – myelinated or unmyelinated axons? 2.Which do you think would conduct an AP faster – an axon with a large diameter or an axon with a small diameter? The answer to #1 is a myelinated axon. Could you move 100ft faster if you walked heel to toe or if you bounded in a way that there were 3ft in between your feet with each step? The answer to #2 is an axon with a large diameter. Could you move faster if you walked through a hallway that was 6ft wide or if you walked through a hallway that was 1ft wide?

Regents Biology Human brain

Regents Biology Diagram of Human Brain Cerebrum Corpus callosum Cerebellum Thalamus Hypothalamus Midbrain Pons Medulla oblongata Spinal cord

Regents Biology Primitive brain Functions basic body functions breathing, heart, digestion, swallowing, vomiting homeostasis coordination of movement The “lower brain” medulla oblongata ponscerebellum

Regents Biology Higher brain Cerebrum 2 hemispheres left controls right side of body right controls left side of body Corpus callosum connection between 2 hemispheres

Regents Biology Division of Brain Function Left hemisphere “logic side” language, math, logic operations, vision & hearing details fine motor control Right hemisphere “creative side” pattern recognition, spatial relationships, non-verbal ideas, emotions, multi-tasking

Regents Biology Cerebrum Regions specialized for different functions Lobesfrontal speech, control of emotions temporal smell, hearing occipitalvisionparietal speech, taste reading frontal temporaloccipital parietal

Regents Biology Limbic system Controls basic emotions (fear, anger), involved in emotional bonding, establishes emotional memory

Regents Biology Simplest Nerve Circuit  Reflex, or automatic response  rapid response  automated  signal only goes to spinal cord  no higher level processing  advantage  essential actions  don’t need to think or make decisions about  blinking  balance  pupil dilation  startle

Regents Biology What do you think can change neurons and their connections? AccidentsDrugsAlcohol Disease (Contagious and hereditary) iction/drugs/mouse.html

Regents Biology What if neurons die here? or here

Regents Biology Parts of the Brain Occipital lobe- visual processing Temporal lobe-memory, sound processing, auditory stimuli Frontal lobe- higher thought functions, judgment, personality, emotion, problem-solving, planning, movement Parietal lobe- sensation, language (left side) Pons- breathing, relay

Regents Biology Parts of the brain continued… Medulla oblongata- heart rate, respiratory, blood flow Thalamus- sensory integration + motor integration Hypothalamus- body temperature, emotion, hunger, thirst, appetite, digestion, sleep Cerebellum- balance, posture, coordination, novelty emotions