General Physiology - Neurons and Action Potential PDF

UE| BS PSYCH GENERAL PHYSIOLOGY / PROF. STEVE OBANAN NEURONS AND ACTION POTENTIAL, CENTRAL NERVOUS SYSTEM Stimulates contraction (or inhibits BASIC CONCEPTS: NEURONS contraction) o...

UE| BS PSYCH GENERAL PHYSIOLOGY / PROF. STEVE OBANAN NEURONS AND ACTION POTENTIAL, CENTRAL NERVOUS SYSTEM Stimulates contraction (or inhibits BASIC CONCEPTS: NEURONS contraction) of smooth muscles and cardiac muscle and stimulates ❖ NEURONS glandular secretion. Nerve cells Sympathetic ❖ CELL BODY / SOMA Parasympathetic Nucleus ❖ 2 Processes / extension Dendrite - impulse to the soma SUPPORTING CELLS (CNS) Axon - impulse away from the soma ❖ Oligodendrocytes ❖ TYPES: Form myelin sheaths around axons of the Structure CNS Unipolar - 1 extension ❖ Microglia Bipolar - 2 extensions Migrate through the CNS and Multipolar - many dendrites and axon phagocytose foreign material Function: ❖ Astrocytes Sensory / afferent - receptors impulses Help to regulate the external environment to CNS of neurons in the CNS Motor / efferent - from CNS to effector ❖ Ependymal cells (muscle / gland) Line in the brain ventricles (cavities) of the Association / interneuron - connects 2 brain and the central canal of the spinal types cord ADDITIONAL NOTES SUPPORTING CELLS (PNS) ❖ Meninges ❖ Schwann cells (neurolemmocytes) Dura mater Form myelin sheaths around peripheral Pia mater axons Arachnoid ❖ Satellite cells (ganglionic gliocytes) ❖ NERVOUS SYSTEM Support neuron cell bodies within the CNS (CENTRAL NERVOUS SYSTEM) ganglia of the PNS Brain and Spinal Cord PNS (PERIPHERAL NERVOUS TERMINOLOGIES SYSTEM) Somatic (motor nerve) ❖ Nerve Stimulates contraction of skeletal Bundle of axons in the PNS; may contain muscle both sensory and motor fibers Autonomic (motor nerve) ❖ Ganglion BS PSYCH ANDRES 09 - 28 - 24 1  GENERAL PHYSIOLOGY | NEURONS AND ACTION POTENTIAL, CENTRAL NERVOUS SYSTEM Grouping of neuron cell bodies located outside the CNS ❖ Nucleus Grouping of neuron cell bodies within the FACTORS IN ACTION POTENTIAL CNS; not same as cell nucleus (PROPAGATION) ❖ Tract ❖ Amount of myelination Grouping of axons that interconnect ❖ Axon diameter regions of the CNS ❖ Temperature RESTING MEMBRANE POTENTIAL ADDITIONAL NOTES ❖ Constant membrane potential in excitable ❖ Continuous Conduction and non excitable cells under resting The axon potential travels to the axon;and conditions travels throughout the extension of the ❖ Inside is negatively charged with respect to neuron. the outside ❖ Saltatory Conduction -5 to -100mV (most cells) This will make the transmission of -70mV for neurons impulses faster than the continuous ❖ Steady transmembrane potential that is not conduction. producing electrical signal REFRACTORY PERIODS ACTION POTENTIAL ❖ This are time or periods wherein you cannot ❖ Large rapid alterations in the membrane have another action potential potential ❖ Absolute Refractory Period ❖ May change 100mV and repolarize to its If there is happening action potential; no resting potential action potential can happen ❖ Happens excitable membranes ❖ Relative Refractory Period No action potential can happen; however MECHANISM OF ACTION POTENTIAL if the stimulus is greater and can generate ❖ Resting membrane potential is close to K+ another action potential it may cause Eq because of K+ leak channels another action potential. But the stimulus ❖ Depolarizing stimulus - opens the should be greater than the usual one voltage-gated Na+ channels being generated. ❖ Membrane reaches the threshold potential; depolarization becomes positive feedback —///////////////////////////////////////////////////////////////////////////— ❖ Large upstroke of membrane potential and overshoots. CENTRAL NERVOUS SYSTEM ❖ Outward current of K+ through voltage gated ❖ Cerebrum channels repolarizes the membrane Largest portion of the (80% of its mass) ❖ Slowly closing voltage-gated K+ channels Consisting of five paired lobes within two causes hyperpolarization, Na+ channels convoluted hemispheres closed from inactivated state Contains gray matter in its cortex and ❖ Closed voltage-gated K+ channels returns deeper cerebral nuclei the membrane potential to RMP BS PSYCH ANDRES 09 - 28 - 24 2  GENERAL PHYSIOLOGY | NEURONS AND ACTION POTENTIAL, CENTRAL NERVOUS SYSTEM Cerebral cortex - 2 to 4 mm of gray ❖ Receive input from the cerebral cortex and matter and underlying white matter provide output to motor parts of the cortex Numerous folds and grooves via thalamus (convolutions) ❖ Help regulate initiation and termination of Elevated - gyrus; grooves - sulcus movements ❖ Help regulate initiation and termination of LOBES OF THE CEREBRUM movements ❖ Control subconscious contractions of skeletal ❖ Frontal Lobe muscles Anterior portion of each cerebral ❖ Neuronal activities in: hemisphere Putamen precedes or anticipates body Voluntary motor control of skeletal movements muscles; personality; higher intellectual Caudate nucleus occurs prior to eye processes; verbal communication movements ❖ Parietal Lobe Somatesthetic interpretation Understanding speech and formulating LIMBIC SYSTEM words ❖ Someone called the “emotional brain” plays Interpretation of textures and shapes a primary role in a range of emotions, ❖ Temporal Lobe including pain, pleasure, docility, affection Contains auditory centers that receive and anger auditory information ❖ Involved in olfactory and memory Interpretation an association of auditory ❖ Components: and visual information Cingulate gyrus (part of the cerebral ❖ Occipital Lobe cortex) Visual perception and coordination of eye Amygdala movements Hippocampus Correlation of visual images with previous Septal nuclei visual experiences and other sensory stimuli CEREBRAL CORTEX ❖ Processes specific types of sensory, motor, BASAL NUCLEI and integrative signals ❖ Also known as Basal Ganglia - masses of ❖ Sensory areas - receive sensory information gray matter and re involved perception ❖ Composed of neuron cell bodies located ❖ Motor areas - control the execution of deep in the white matter of the cerebrum voluntary movements ❖ Basal Nuclei lie side by side, just lateral to ❖ Association areas - deal with more complex the thalamus - globus pallidus and putamen integrative functions such as memory, (lentiform nucleus) emotions, reasoning, judgment, personality ❖ Third of the basal nuclei - caudate nucleus traits, intelligence ❖ Function in the control of voluntary movements BS PSYCH ANDRES 09 - 28 - 24 3  GENERAL PHYSIOLOGY | NEURONS AND ACTION POTENTIAL, CENTRAL NERVOUS SYSTEM CEREBRAL CORTEX (SENSORY AREAS) CEREBRAL CORTEX (MOTOR AREAS) CEREBRAL CORTEX (ASSOCIATION AREAS) DIENCEPHALON ❖ Forms a central core of brain tissue just superior to the midbrain ❖ Contains numerous nuclei involved in a wide variety of sensory and motor processing between higher and lower brain centers ❖ Includes the thalamus, hypothalamus, and epithalamus BS PSYCH ANDRES 09 - 28 - 24 4  GENERAL PHYSIOLOGY | NEURONS AND ACTION POTENTIAL, CENTRAL NERVOUS SYSTEM MIDBRAIN (MESENCEPHALON) THALAMUS ❖ Located between the dience[halon and the pons, containing nuclei and tracts ❖ Corpora quadrigemina Four rounded elevations on the dorsal surface Superior colliculi Coordinate movements in response to visual stimuli Inferior colliculi Relay center for auditory information ❖ Cerebral peduncles Ascending and descending fiber tracts Conduct nerve impulses from motor areas EPITHALAMUS in the cerebral cortex to the spinal cord, medulla, and pons ❖ Cerebral aqueduct Passes through the midbrain, connecting the third ventricle above with the fourth ventricle below ❖ Substantia nigra and red nucleus Contribute to control of movement CEREBELLUM ❖ Posterior to the medulla and pons; inferior to the posterior portion of the cerebrum ❖ Second largest structure of the brain containing about 50 billion neurons HYPOTHALAMUS ❖ Receives input from proprioceptors (joint, tendon and muscle receptors) ❖ Participates in the coordination of movement (with basal nuclei and cerebral cortex) ❖ Evaluate how well movements are actually being carried out ❖ Regulates posture and balance PONS ❖ Rounded bulge on the underside of the brain, between the midbrain and the medulla oblongata ❖ Pontine nuclei relay nerve impulses from motor areas of cerebral cortex to cerebellum BS PSYCH ANDRES 09 - 28 - 24 5  GENERAL PHYSIOLOGY | NEURONS AND ACTION POTENTIAL, CENTRAL NERVOUS SYSTEM ❖ Pontine respiratory group (together with the medulla) helps control breathing MEDULLA OBLONGATA ❖ Continuous with the pons superiorly and the spinal cord inferiorly ❖ Inferior part of the brain stem (about 3cm) ❖ With groupings of neurons (vital centers): Vasomotor center Controls the autonomic innervation of blood vessels Cardiac control center Regulates the autonomic nerve control of the heart Respiratory center Acts together with centers in the pons to control breathing ❖ Other nuclei coordinate vomiting, swallowing, sneezing, coughing, and hiccuping ❖ Functions in consciousness and arousal BS PSYCH ANDRES 09 - 28 - 24 6