Biological basis of behavior: Nervous system

• Central Nervous System: Brain and spinal cord, controls all body functions
• Brainstem: the part of the brain stem that connects the brain to the spinal cord
• Parts of the brainstem: Midbrain, Pons, Medulla
• Cerebrum: consist of two hemispheres, left and right, separated by a fissure. It is responsible for the integration of complex sensory and neural functions and the initiation and coordination of voluntary activity in the body.
• Cerebellum: controls muscle coordination, balance, and posture.
• forebrain/ prosencephalon: becomes cerebrum
• midbrain/ mesencephalon: becomes midbrain
• Hindbrain/ rhombencephalon: becomes cerebellum
• Peripheral Nervous System: contains nerves and ganglia
• cranial nerves: exit the skull to the body
• spinal nerves: exit the spinal cord to the body
• ganglia: clusters of neurons that connect to other neurons and form a network
• afferent neurons: neurons that carry information away from the PNS to the CNS
• efferent neurons: carry impulses away from the CNS to the effector organs
• Basic functions of the brain: motor, sensory, and autonomic
• Higher functions of the brain: consciousness, emotion, and cognition
• Motor units: A group of muscle fibers that work together to produce a single movement.
• lower motor neurons: efferent neurons that control skeletal muscle through synapses of neurons
• neuromuscular junction: the point where a motor neuron synapses with a muscle cell
• All somas of lower motor neurons are located in the CNS and the axons will pass through cranial nerves or spinal nerves
• small muscles= smaller motor units
• large muscles= larger motor units
• Abnormalities of lower motor units: hyporeflexia, fasciations, hypotonia, general weakness, atrophy
• atrophy: decrease in the muscle size
• fasciations: muscle twitching
• Hypotonia: decreased muscle tone
• hyporeflexia: decreased muscle stretch reflex
• muscle stretch reflex: when a muscle is stretched, the muscle spindles send impulses to the spinal cord
• muscle spindles: detect stretch and tension of muscle, send signals to spinal cord
• Types of mechanoreceptors: position, vibration, touch
• Nociceptors and thermoreceptors usually have bare nerve endings
• Proprioceptors, mechanoreceptors, and fine touch receipts: have large diameters and thick myelin sheaths. They fire fast action potentials.
• Nociceptors, thermoreceptors, and gross touch receipts have small diameters with thin myelin sheaths. They fire slow action potentials
• efferent neurons control: smooth muscle, skeletal muscle, and gland cells
• sympathetic nervous system nerves are located in the middle of the spinal cord. The first axon is short followed by a longer axon then the target organ
• Parasympathetic nervous system nerves start in the brainstem or the bottom of the spinal cord. The first axon is long followed by a shorter axon then the target organ
• Sympathetic nervous system in the GI tract: decreases blood flow in intestines
• Parasympathetic nervous system in the GI tract: increases blood flow to the intestines
• Sympathetic nervous system in the heart: Increases heart rate and contractility
• Parasympathetic nervous system in the heart: slows heart rate and contractility