The Nervous System AP Biology Grant Rosensteel Zenora

The Nervous System AP Biology Grant Rosensteel & Zenora Saelua

Overview • The nervous system gives us our personality, emotions, enables memory, and allows us to respond to stimuli. • The Nervous system consists of Neurons, Glial cells, nerves, and sensory receptors.

Structure • Neurons have 4 regions- cell body, dendrites, axon, and axon terminals. • Cell body: most organelles and supporting structures. • Dendrites: extensions of the cell body which receive signals from nearby neurons. • Axon: long projection that carries the action potential “telephone lines”. • Axon Terminals: ending of axon, where it swells that produces neurotransmitters. • Nerve: bundle of axons.

Synapses • Space between two neurons in which they communicate. • Communicate using neurotransmitters (chemical signaling molecules). • Neuron sending the information: presynaptic. • Neuron receiving the information: postsynaptic. • The receiving of neurotransmitters results in the creation of an action potential in the postsynaptic neuron.

Action Potentials • Electric signals. • Formed when a stimulus causes the cell membrane to depolarize past the excitation threshold which allows sodium gates to open. • Action potentials travel down the axon as the membrane of the axon depolarizes.

Glial Cells • Other cells of nervous system; they support, nourish, and insulate neurons. • More of these than neurons • Can physically support and orient neurons in development. • Astrocytes: surround smallest blood vessels in brain, create blood-brain barrier which prevents toxins from reaching brain. • Microglia: act as macrophages and mediators of inflammation.

Glial cont. • Insulate axons with oligodendrocytes. • Myelin sheath is created by Schwann Cells. • White matter: heavily myelinated neurons • Gray Matter: rich in cell bodies and not axons. • Multiple Sclerosis: disease that demyelinates axons, impairs ability to fire action potentials.

Neural Networks • Information processing networks • Afferent: carry sensory information into nervous system. Contain specialized cells that convert sensory stimuli into action potentials. • Efferent: carry physiological and behavioral effectors to muscles and glands. • Interneurons: integrate and store information and communicate between afferent and efferent neurons.

Neuromuscular Junctions • Synapses between motor neurons and skeletal muscles. • Each axon terminal ends in a bouton that contains vesicles filled with neurotransmitters. (Acetylcholine) • ACh is released when action potential reaches end of axon. • Causes the opening of Ca 2+ channels which allow them to enter cell • Increased Ca 2+ causes vesicles filled with ACh to fuse with membrane via exocytosis.

Vertebrate Nervous System • Divided into Central Nervous System (CNS) and Peripheral. • CNS: brain and spinal cord • PNS: All other neural cells

PNS • Divided into Autonomic and Somatic • Autonomic: output of pathways of CNS and control involuntary functions • Somatic: controls voluntary muscles

ANS • Divided into sympathetic and parasympathetic • Sympathetic: arousal mechanisms, flight or flight, raising bp, and heart rate. • Parasympathetic: calming, rest and digest, slows heart, lowers bp

Brainstem • All information travels between spinal cord and higher brain goes through it. • Comprised of pons, medulla, and midbrain • Controls basic life functions: respiration, heart rate, bp

Limbic System • Very old part of the brain responsible for many basic life functions and instinctive responses. Pain, fear, pleasure, rage, memory formation. • Amygdala: center for fear reactions and fear memories • Hippocampus: necessary for transfer of short term memory to long term.

Brain • Cerebrum: dominant structure of brain (wrinkly part). • Two hemispheres (left and right) • Cerebral Cortex: outermost layer of brain, folded into convolutions that increase surface areas. • 4 lobes: temporal, frontal, parietal, occipital

Temporal • Receives and processes auditory information, visual processing. • Recognizing, identifying, and naming objects

Frontal • Largest lobe • Associated with: feeling and planning, contributes to our personality • Contains primary motor cortex which controls muscle movements.

Parietal Lobe • Attends to complex stimuli • Helps translate visual information into perception of objects in a 3 D space. • Contains primary somatosensory cortex, receives touch and pressure information.

Occipital Lobe • Receives and processes visual information. • Translating visual experience into language

Complex Abilities in Humans • Ability to extensively use and manipulate language and to learn and remember. • Differentiates us from lower primates

Language • Localized in left cerebral hemisphere (phenomenon known as brain lateralization of functions. ) • Broca’s Area: in frontal lobe, essential for production of language (muscular formation of words) • Wernicke’s Area: temporal lobe, understanding language.

Learning • Modification of behavior by experience. • To learn one must convert memories to long term memory through long lasting synaptic changes. • Long term potentiation: high frequency electrical stimulation of certain neural circuits making them more sensitive to stimulation. • Associative: type of learning where two unrelated stimuli become linked to same response • Conditioned reflex: Pavlov’s dog; reflex would be conditioned to certain stimuli (salivation at ringing of the bell. )

• Observational learning is the foundation of human intelligence. • Pay attention to another person’s behavior • Retain memory of what has been observed • Attempt to copy or use the information

Memory • Declarative: memory of facts (people, places, events) that you can recall and describe. • Procedural: memory of how to perform a certain motor function (ride a bike) • Repetition of short term memory moves it to long term.

Sleep • Lack of results in: decline in alertness, impaired learning, immune suppression, hormonal changes etc. • Use EEG to monitor sleep patterns. • 2 Stages: REM and non REM • We fall asleep when the resting potentials of neurons are no longer close to the threshold so they are no longer easily stimulated • Happens because less neurotransmitters are released.