Chapter 48-49

The anatomy of a neuron. The mechanisms of impulse transmission in a neuron. The process that leads to release of neurotransmitter, and what happens at the synapse. The components of a reflex arc and how they work. The organization and function of the major parts of the nervous system. One function for each major brain region. The location and function of several types of sensory receptors. How skeletal muscle contracts. Cellular events that lead to muscle contratction

Functional unit of the nervous system Dendrites: cell extensions that receive incoming messages from other cells Axon: transmit messages to other cells Covered in myelin sheath (Schwann cells or oligodendrocytes) to speed up transmission Synapse: is the junction between axons and dendrites Neurotransmitters (NT): chemical messengers (drugs) released from the synaptic terminals of the axon which bind to receptors of the receiver (another neuron, muscle cell, or gland) Acetylcholine, dopamine, serotonin, GABA, etc.

Central nervous system (CNS) = brain & spinal cord Peripheral nervous system (PNS) = everything else including motor and sensory neurons Nerves are clusters of neurons Types of neurons: Sensory receptors: receive information from the environment Sensory neurons: send signals from receptors to CNS Interneurons: brain and parts of the spinal cord Motor neurons: transmit signals to effectors (muscles, glands)

Membrane potential: difference in electrical charge across the cell membrane Resting potential: neuron at rest (-70mV)

All or none response to stimulus If membrane potential reaches threshold (- 55mV) AP will fire 1.Resting state 2.Depolarization 3.Depolarization >= threshold  AP 4.Repolarization 5.Undershoot

APs propagate down the axon It jumps from one node of Ranvier to the next (saltatory conduction) The signal is revitalized at every node At the synapse the signal continues via electrical or chemical (NT) stimulus Stimulus can be inhibitory or excitatory

Simplest response to stimulus Receptor  sensory neuron  interneuron (spinal cord)  motor neuron  effector (reaction) The brain finds out later

Brain and spinal cord Cells bathed in cerebrospinal fluid (CSF) for nutrients and cleansing Grey matter = neuron cell bodies and unmyelinated axons White matter = myelinated axons Neural glial cells (glia) support neurons: Astrocytes provide nutrients for neurons Oligodendrocytes make myelin sheath in the CNS (Schwann cells in the PNS)

Divided into two subdivisions: 1.Somatic nervous system: muscles you control 2.Autonomic nervous system: automatic muscle and organ control subdivided into two more categories 1.Sympathetic division: fight or flight mechanism 2.Parasympathetic division: rest and digest

Compartmentalized: Brainstem = medulla oblongata, pons, and midbrain Primitive brain = primitive functions like homeostasis and breathing Cerebellum: coordinated motor movement Thalamus: main center for all sensory and motor information Hypothalamus: regulates homeostasis and basic survival behaviors Cerebrum: two hemispheres with grey over white matter Cerebral cortex: Higher order thinking occurs here (largest in mammals) and voluntary movement Corpus callosum: white matter enabling communications of the two hemispheres

Perception: brain recognition of stimulus Reception: receptor detects a stimulus Mechanoreceptors: stimulated by physical stimuli Thermoreceptors: stimulated by temperature Chemoreceptors: chemical stimulation (taste and smell) Electromagnetic receptors (photoreceptors): detect various forms of energy (light, electricity, or magnetism) Pain receptors: detect too much heat or chemicals released from dying cells