Cells Endocrine System Nervous System Tissues Controls Organs
Nervous System vs Endocrine System Electrical signals (graded potentials and action potentials) and chemical signals (neurotransmitters) Fast acting Short-lived Chemical signals (hormones) that travel in the blood Slow response Long lasting
The Basic Jobs of the Nervous System Sensory input Integration Motor output
2 BIG Divisions Central Nervous System Brain & Spinal cord Peripheral Nervous System Outside the CNS (outside the DBC) Cranial Nerves & Spinal Nerves
2 Big Divisions of the PNS Sensory Afferent Motor Efferent S A M E
Motor Efferent Divisions Somatic Nervous System Controls skeletal muscle Mostly voluntary Autonomic Nervous System Controls cardiac and smooth muscle Involuntary
Autonomic NS Divisions
Cells of Nervous Tissue Neurons Glial cells
Functions of Neurons Sending signals from sensory organs to CNS (Sensory input) Integration Sending signals from CNS to effector organs (Motor output)
Glial Cells
Typical Neuron = Cell w/ several processes Cell body Dendrites Dendrites + Axon Axon
Nucleus Nissl body Soma Neurofibrils
Soma
Nucleus Collection of somata in the CNS
Ganglion Collection of somata in the PNS
Dendrites Receive signals from other neurons/sensory organs Send electrical signals (graded potentials) to the soma and the axon Usually multiple
Receive electrical signals (graded potentials) from dendrites/soma Send electrical signals (action potentials) to the axon terminal Axon terminal releases neurotransmitters onto another neuron or an effector cell Node of Ranvier Axon terminals (secretory region) Axon hillock Axon Neurilemma Schwann cell Telodendri
Synapse = Junction btwn 2 neurons or btwn a neuron and an effector cell
Synapse Presynaptic neuron Axon terminal Synaptic vesicles Postsynaptic neuron
Structural Classification of Neurons Multipolar Bipolar Unipolar
Multipolar Neurons
Bipolar Neurons
Bipolar Neurons
Unipolar Neurons
Functional Classification of Neurons Stimulus 1 Receptor Interneuron 2 Sensory neuron 3 Integration center 4 Motor neuron 5 Effector Spinal cord (CNS) Response
Membrane Potential = Electrical difference btwn the inside of a cell and the outside Voltmeter Plasma membrane Ground electrode outside cell Microelectrode inside cell Axon Neuron
Establishing a Membrane Potential Outside cell Inside cell
Establishing a Membrane Potential K+ leakage channels K K+ K+ + + K Cell interior 90 mv
Establishing a Membrane Potential K+ K+ Na+ K+ K+ + Na Cell interior 70 mv
Polarized Voltmeter Plasma membrane Ground electrode outside cell Microelectrode inside cell Axon Neuron
Electrical signals carry info from one end of a neuron to the other. These electrical signals are waves of change in the membrane potential.
Changing the Membrane Potential
Depolarization -70mV
Hyperpolarization -90 mv
Threshold, EPSPs, and IPSPs -70mV -90 mv
Graded Potentials Waves of change in the membrane potential in the dendrites and soma. Get smaller with distance.
Action Potentials Waves of change in the membrane potential in the axon. Does not get smaller with distance. All-or-none.
Graded Potentials
Graded Potentials
Graded Potentials Action Potentials
Threshold Potential
Temporal Summation
Spatial Summation
Action Potential
Action potentials Threshold Stimulus Time (ms)
1 2 3 4 5 6 +30 +10 0 mv 10 Voltagegated Na+ channels are open. 2 Graded potentials reach threshold 3 Depolarization 4 Repolarization 5 Hyperpolarization 6 Return to RMP Voltage-gated K channels are open. Potential below RMP Threshold 70 90 RMP + 30 50 1 Resting membrane potential Time (ms ec )
Sodium channel Na+ Potassium channel Activation gates Inactivation gate 1 Resting state K+
Na+ K+ 2 Depolarizatio n
Na+ K+ 3 Repolarizatio n
Na+ K+ 4 Hyperpolarization
Absolute refractory period 1 2 3 Relative refractory period 4 5 6 +30 +10 0 mv 10 Voltagegated Na+ channels are open. 2 Graded potentials reach threshold 3 Depolarization 4 Repolarization 5 Hyperpolarization 6 Return to RMP Voltage-gated K channels are open. Potential below RMP Threshold 70 90 RMP + 30 50 1 Resting membrane potential Time (ms ec )
Action Potential
Depolarization: Consecutive voltage-gated Na+ channels go through the following stages: open, closed (inactivation state), closed (resting state) Interstitial fluid Na+ + + + + + + + + + + + + + + Cytosol Closed (resting state) Closed (inactivation state) + + +30 mv + + + + + + + + + + 55 mv Open (activation state) As threshold is reached Na+ channels open and Na+ diffuses in; polarity reversed 70 mv Closed (resting state)
Repolarization: Consecutive voltage-gated K+ channels go through the following stages: open and closed K+ + + + + + + + + + + + + Closed 70 mv + + + + + + + + + + + + Open +30 + + + + + mv Closed K+ channels open and K+ diffuses out; RMP ( 70 mv) is reestablished
Absolute refractory period 1 2 3 Relative refractory period 4 5 6 +30 +10 0 mv 10 Voltagegated Na+ channels are open. 2 Graded potentials reach threshold 3 Depolarization 4 Repolarization 5 Hyperpolarization 6 Return to RMP Voltage-gated K channels are open. Potential below RMP Threshold 70 90 RMP + 30 50 1 Resting membrane potential Time (ms ec )
Continuous Conduction of an Action Potential Stimulus Voltage-gated ion channel
Saltatory Conduction of an Action Potential Myelin sheath Stimulus Node of Ranvier 1 mm Myelin sheath
Neurotransmitter Release Presynaptic neuron Presynaptic neuron Postsynaptic neuron 1 Action potential arrives at axon terminal. 2 Voltage-gated Ca2+ channels open and Ca2+ enters the axon terminal. Ca2+ Ca2+ Mitochondrion Ca2+ Ca2+ 3 Ca2+ entry causes neurotransmittercontaining synaptic vesicles to release their contents by exocytosis. Axon terminal Synaptic cleft Synaptic vesicles 4 Neurotransmitter diffuses across the synaptic cleft and binds to specific receptors on the postsynaptic membrane. Postsynaptic neuron
Neurotransmitter Disposal