Lab 1 Nervous System - University of Guelph

Lab 1 Nervous System OVERVIEW OF THE SKULL, MENINGES AND VENTRICLES Ventricles Meninges Dura Mater Arachnoid Sub-Arachnoid Pia Mater CSF CSF Lab 1 Nervous System OVERVIEW OF THE BRAIN Overview Cerebrum...

Lab 1 Nervous System OVERVIEW OF THE SKULL, MENINGES AND VENTRICLES Ventricles Meninges Dura Mater Arachnoid Sub-Arachnoid Pia Mater CSF CSF Lab 1 Nervous System OVERVIEW OF THE BRAIN Overview Cerebrum Diencephalon “intermediate brain” Cerebellum “Little brain” Brain Stem “Ancient brain” Cerebrum Cerebral cortex Cerebral cortex White matter (myelinated axons) Grey matter (nerve cell bodies) Basal nuclei Diencephalon Epithalamus Diencephalon Epithalamus Thalamus Diencephalon Epithalamus Hypothalamus Diencephalon Epithalamus Pituitary Diencephalon Epithalamus Pituitary Lab 1 Nervous System OVERVIEW OF THE VERTEBRAE AND SPINAL CORD The Atlas (left) and Axis (right) Vertebral column cervical Thoracic Lumbar Sacral coccygeal Vertebral flexibility The vertebral column Muscles and Ligaments Intervertebral discs Individual vertebra Transverse process Individual vertebra Spinal cord. Grey matter Central canal (CSF) White matter Spinal cord Spinal cord Dorsal Root= Sensory Neuron Flow of information: Arrives to the CNS = Afferent Exits the CNS = Efferent Ventral Root= Motor Neuron Spinal cord Meninges Medical Applications – EpiduralMeninges Injection Medical Applications – Spinal Tap Meninges Used to diagnose CNS issues such as.... Meningitis Subarachnoid hemorrhages Encephalitis Guillain-Barre Syndrome Multiple sclerosis Lab 1 Nervous System REVIEW OF ACTION POTENTIAL  Meninges Resting Membrane Potential (RMP) RMP: results from a difference in charge across the cell membrane ◦ Average RMP in a nerve cell around -70 to -90 mV Ways to maintain RMP: 1. Selective permeability (diffusion) 2. Ion Pumps 3. Large anions trapped on the inner surface of membrane  Meninges 1. Selective Permeability (diffusion) CELL WALL Passive leakage of ions through channels Concentration gradient Resting membrane is permeable to K+, barely permeable to Na+, Ca2+ and Cl- Therefore, positive charges accumulate outside 2. Ion pumps Concentration of ions remains relatively constant inside the cell Compensates for diffusion leakage Na+/K+ pump: for every 3 Na+ pumped out, 2 K+ are brought in Requires a lot of energy Up to 40% of available ATP 3. Large anions trapped on the inner surface of membrane Organic anions mostly in proteins and amino acids Found in higher concentrations inside the cell Cannot pass through the membrane freely Attracted to the outside positive charges Excitable Cells Cells that can generate electrical impulses (action potentials) Can change their membrane polarity ◦ Use specialized ion channels with gates that open and close ◦ In nerve cells the gate is controlled by voltage (voltage-gated ion channels) At rest, the gate is closed ◦ Gates need stimulation (voltage) to reach threshold provoking the opening of the gate Generation of Action Potentials (AP) in Neurons 1. Depolarization: initial depolarization (stimulation) reaches threshold provoking the opening of Na+ voltage-gated channels ◦ Influx of Na+ ◦ After ~0.5 ms, Na+ channels close rapidly 2. Repolarization: K+ voltage-gated channels then open ◦ Outflow of K+ 3. Hyperpolarization (afterhyperpolarization): K+ voltage-gated channels progressively close ◦ Excess outflow of K+ 4. Refractory Period: RMP restored through diffusion and Na+/K+ pumps ◦ Neurons cannot be restimulated until restored  1 2 3 4 Potassium Sodium Synaptic Transmission Continuation of signal between a neuron and the following cell (another neuron or target cell) ◦ Neuronal junction: transmission between two neurons ◦ Neuromuscular synapse: transmission between a neuron and skeletal muscle cell Cell membrane made of phospholipids = electric insulator Neurotransmitter: molecule responsible for passing the information ◦ Neuromuscular synapse transmitter: Acetylcholine (ACh) ◦ Convert the electrical signal (AP) into a chemical signal Post-synaptic folding is common in neuromuscular synapse to increase surface area General Mechanism of Action (in neuromuscular synapse) 1. Action Potential in pre-synaptic neuron 2. Action Potential opens voltage-gated Ca2+ channels ◦ Influx of Ca2+ 3. Ca2+ triggers exocytosis of Acetylcholine (Ach) 4. ACh diffusion in the cleft 5. ACh binds to specific receptors 6. Depolarization of post-synaptic cell: ◦ Na+ channels open on post-synaptic membrane ◦ Na+ then flows into the cell 7. Neurotransmitter inactivated ◦ termination of signal