Chapter 12 PowerPoints

• Review the key roles of transmembrane channel and carrier proteins in determining and maintaining transmembrane potential, as well as rapid changes in the resting membrane potential (action potentials).

• Passive (Leak) Channels o Always open o Permeability changes under different conditions • Active (Gated) Channels o Open and close in response to stimuli o When the membrane is at resting potential, most gated channels are closed • ANY STIMULUS THAT OPENS A GATED CHANNEL PRODUCES A GRADED POTENTIAL

• Describe the various phases of the action potential (including the relative and absolute refractory periods) and associated key structural components of the neuron that contribute to the changes in membrane potential for each phase.

1. Start at resting membrane potential when charges are separated. Na+ on the outside and K+ on the inside. 2. Stimuli on the membrane cause graded potentials, which, cause a temporary localized change in resting potential. 3. If enough graded potentials add up to the threshold value, an action potential (electrical impulse) is produced and continues to travel down the neurons axon on the way to the synapse. 4. Once that electrical impulse reaches the axon terminals neurotransmitters are released which cross the synaptic cleft to produce graded potentials on the postsynaptic membrane 5. That postsynaptic cell will then respond by integrating the stimuli

• Describe the differences in anatomy, location, and function of unipolar, multipolar, and bipolar neurons.

A). Anaxonic neurons have more than two processes, and they are all dendrites. B) Bipolar neurons have two processes separated by the cell body C). Unipolar neurons have a single elongated process, with the cell body located off to the side. D). Multipolar neurons have more than two processes; there is a single axon and multiple dendrites. • Bipolar used by special senses • Multipolar found in the brain/spinal cord o All motor neurons from the . . CNS are multipolar o Interneurons in the CNS. • Unipolar Cell body (SOMA) grouped together in a sensory ganglia. • These are Afferent nerve fibers because they ASCEND to the central nervous system (brain and spinal cord)

• Identify the key structural features of the neuron and describe their specific functions.

Axon: The elongated extension of a neuron that conducts an action potential. Axon hillock: In a multipolar neuron, the portion of the cell body adjacent to the initial segment Axon Terminal: is part of a synapse, a specialized site where the neuron communicates with another cell Dendrite: A sensory process of a neuron Nodes Of Ranvie: The small gaps of a few micrometers that separate adjacent internodes Telodendria: Terminal axonal branches that end in axon terminals CellBody Perikaryon: The cytoplasm that surrounds the nucleus in the cell body of a neuron Nucleus: A cellular organelle that contains DNA,RNA, and proteins; in the central nervous system , a mass of gray matter Schwann Cells: Neuroglia responsible for the neurilemma that surrounds axons in the peripheral nervous system; also called neurilemma myelin: An insulating sheath around an axon; consists of multiple layers of neuralgia membrane; significantly increases the nerve impulse propagation rate along the axon

• Describe the structural and functional subdivisions of the nervous system including sensory/afferent, motor/efferent, interneurons, somatic, visceral/autonomic, central, and peripheral nervous systems.

Central(CNS)-The spinal cord and brain o. important for processing sensory data and . sending out motor commands o Also important for higher functions of brain . intelligence like intelligence, memory, learning and emotion Peripheral (PNS)-All neural tissue outside the CNS o Important forgetting the sensory data to the . brain and for receiving commands 3 Neuron Functions • Sensory-Afferent-Sensation • Motor-Efferent-Movement • Interneurons-go between 2 neurons • Monitor the internal and external environment o Internal-Visceral sensory-interoceptors o External-SomaticSensory-exteroceptors o Proprioceptors-monitor position and movement of muscle and joints

• Describe the key components and events involved in transmission of action potentials across a cholinergic synapse.

Cholinergic synapses • Is any synapse that releases acetylcholine. • Found at: o Neuromuscular junctions between the nerve and the skeletal muscle fiber o Quite a few synapses with in the CNS o AllNeuron-Neuron synapses in the PNS o All Neuromuscular and neuroglandnular junctions of the ANS parasympathetic division

• Describe the structural and functional differences between continuous and salutatory propagation of action potentials.

Continuous vs. Saltatory Propagation • Saltatory Propagation o Myelin is the key o Action potential along a myelinated axon will travel faster and use less energy through saltatory propagation • Continuous Propagationo With out myelin the action potential depolarizes the whole axon• Step3- The first segment enters a refractory period o This is important because the action potential is forced to travel in one direction.

• Understand the difference between excitatory and inhibitory postsynaptic potentials (EPSP's and IPSP's) and how temporal and spatial summation, relate to these concepts and information processing.

Excitatory Vs. Inhibitory Potentials • excitatory- >Cause depolarization of post synaptic membranes and promote action potentials •. inhibiyory- > Cause hyper polarization or the post synaptic membrane and suppress action potential1. 1. Depolarization to threshold 2. Activation of Na + channels 3. Inactivation of Na+ channels and activation of K+ channels (repolarization) 4. Return to normal permeability

• Compare and contrast graded versus action potentials and where and how these changes in transmembrane potentials occur on neurons.

Membrane Channels • Chemically gated channels o Open when a specific chemical is at the binding site(e.g.,Ach) o These are found on neuron cell bodies and dendrites • Voltage-gated channels o Respond to changes in membrane potential o Has Activation and inactivation gates o Are responsible for the excitable membrane o Found in neural axons, skeletal muscle sarcolemma, and cardiac muscle • Mechanically gated channels o Respond to membrane distortion o Found in sensory receptors (touch, pressure, vibration)

• Describe the key roles of neurotransmitters at the synapse and be able to provide examples of excitatory and inhibitory neurotransmitters.

Neurotransmitters • Acetylcholine (Ach)Is the one we will talk about most. o Almost always excitatory • Other important neurotransmitters include: o Norepinephrine(NE) • Excitatory • Released at adrenergic synapses o Dopamine • Can be excitatory or inhibitory • Involved in parkinson's disease and the cocaine reward pathway o Serotonin • Affects attention and emotional states o Gamma aminobutyric acid (GABA) and Glutamate • Inhibitory and found in the CNS

• Understand the anatomy of synapses including the structure and roles of the pre- and post-synaptic cells.

Two types of Synapses • Electrical- have a direct connection to another cell • Chemical- signal travels across a gap by chemicals which are called neurotransmitters. o One of the most common types of neurotransmitters is acetylcholine (cholinergic synapse)

• Distinguish between Type A, B, and C neuron fibers both structurally and functionally based on the type of sensory or motor information transmitted by each.

Type A, B, and C neuron fibers • Myelin and a large diameter increases the speed that an action potential travels • TypeAFibers o Myelinated with a large diameter o High Speed(140m/sec) o Important for carrying rapid information to and from the CNS( position, balance, touch, and motor impulses) • Type B Fibers o Myelinated with medium diameter o MediumSpeed(18m/sec) o Important for sensory information and peripheral effectors • Type C fibers o Unmyelinated and small o Slowspeed(1m/sec) o Important for involuntary muscle and gland controls

• Define and differentiate between depolarization and hyperpolarization, as related to membrane potential and the types of ions channels and ion diffusions that contribute to these potential changes.

hyperpolarization: The movement of the membrane potential away from the normal resting potential and farther from 0 mV depolarization: A change in the membrane potential from a negative value toward 0 mV

• Describe the structure, function, and location of neuroglia cells of both central and peripheral nervous systems.

• Take care of the nerves. • They are 50% of the nervous system.1. 1. Ependymal Cells Produce CSF 2. Astrocytes Maintain the Blood Brain Barrier 3. Oligodendrocytes Myelinate CNS Axons Covers Many Axons 4. Microglia Remove cellular debris and waste The macrophage for nervous system1. 5. Satellite Cells Surround the ganglia Regulate the environment around the neuron 6. Schwann cells Form the myelin sheath around the peripheral axons One Covers One Segment of the Axon