AP BIOLOGY 12 - Weebly

AP BIOLOGY 12 - Weebly

BIOLOGY 12 The Nervous System Introduction The Nervous system, along with the Endocrine system, is responsible for integration and control in the body. The nervous system is capable of much more rapid and specific responses than

the endocrine system. The NEURON is the basic cell of the nervous system. It is the most highly specialized cell in the human body. Structure: the neuron is divided into 3 distinct sections; o Cell body contains nucleus and coordinates cell activities o Dendrites carry impulses to cell body o Axons carry impulses away from cell body o Myelin sheath is the fatty substance surrounding parts of the neuron o Schwann cells make the myelin sheath


contain special receptors to detect stimuli Long myelinated dendrites Short axons Cell body outside the spinal cord contained in ganglion Carry impulses toward the CNS

Inter-neurons entire neuron is found inside the spinal cord your brain is made up of all inter-neurons connect the sensory and motor neurons

short dendrites long myelinated axons end of motor neurons are motor end plates attached to muscles Carry message from the brain and spinal cord to muscles and cells

( connector or association neurons) Motor Neurons Nerve Impulses Conduction of the Nerve Impulse Nerve impulses rely on electrical charges which come about from the ionic charges of certain minerals

Membrane potential refers to the neuron POLARITY or difference between the charged ions inside and ouside the neuron. The minerals responsible for all nerve conduction in the body are Na+ K+ and Ca++ Terminology Resting potential refers to the neuron POLARITY or difference between the + outside and inside across the membrane Gated ion channels are found along the neuron membrane

(axomembrane) and allow ions to move in and out of the cell Nerve Impulses Threshold amount of stimulus required to cause the neuron to fire Depolarization when the threshold is met sodium gates open and Na + rushes into cell causing a swing in polarity

Repolarization immediately following the rush of sodium into the cell potassium gate open and K+ rushes out to repolarize neuron Action potential refers to the movement of ions in and out of cell causing a nerve impulse Refractory period all neurons must go through a short rest period and redistribute ions in order to carry out another impulse The Neuron

Along the inside of the membrane are negatively charge organic ions that cant cross the membrane. The effect of this is that the inside is negative and the outside is positive. This produces a membrane potential of about -60 mV. The Neuron 2. The Action Potential

When the impulse reaches any point along the axon, it causes sodium gates to open and Na + floods in. This is due to both a concentration gradient and electrical attraction. This influx of positive ions repels K + which leave as the potassium gates open. The Neuron This depolarizes the axon and this is the

nerve impulse. This depolarization cause the sodium gates immediately adjacent and downstream to open, depolarization now occurs there. This continues as a wave of depolarization along the entire length of the axon. The Neuron 3. Refractory Period (Recovery phase)

As the wave of depolarization moves past, the sodium - potassium pump kicks in again pumping the Na + out and allowing the K + to passively re-enter. This restores the resting potential and the axon can now fire again. Step 1: Resting State. Fig. 48.9

Step 2: Threshold. Fig. 48.9 Step 3: Depolarization phase of the action potential. Fig. 48.9

Step 4: Repolarizing phase of the action potential. Fig. 48.9 Step 5: Undershoot. Fig. 48.9 The Neuron

The impulse jumps from node to node skipping the insulated regions under the myelin sheath. This is termed Saltatory Conduction and greatly speeds up the impulse. Nerve conduction is All or None - if the threshold stimulus is achieved, the impulse will go the entire length of the neuron. Saltatory conduction.

In myelinated neurons only unmyelinated regions of the axon depolarize. Thus, the impulse moves faster than in unmyelinated neurons. The Neural Synapse The junction point between a nerve and any other structure is called a synapse. Pre synaptic cell ends in synaptic knobs that connect to a post synaptic neuron.

In between the two is a space called the synaptic cleft. In the synaptic knob are synaptic vesicles containing neurotransmitter molecules. The Neural Synapse 1. When the impulse reaches the synaptic knob, Ca+2 floods into the knob from the extra cellular environment. 2. This influx causes the pre-synaptic membrane

to be pulled toward the vesicles and fusing to them. 3. This ruptures the vesicles and neurotransmitters floods into the synaptic cleft. The Neural Synapse 4.The neurotransmitter diffuses across the cleft and binds to receptor proteins on the post synaptic membrane.

5. This opens the sodium gates that allows sodium to flood in, initiating the nerve impulse in the second cell. 6. Enzymes quickly break down the attached neurotransmitter to end the transfer. Impulses can only travel in ONE DIRECTION because the vesicles containing neurotransmitters are only found in the AXONS and are responsible tor connecting to the DENDRITES of the adjacent

NEURON. NEURON Neurotransmitters There are two types of neurotransmitters. neurotransmitters Excitatory and Inhibitory If the sum of the excitatory neurotransmitters exceeds the inhibitory neurotransmitters and the THRESHOLD LEVEL has been reached

the neuron will fire. This is also referred to the INTEGRATION of NEURONS. NEURONS Each neuron has a specific TRHESHOLD for EXCITATION. EXCITATION Neurotransmitters are specialized proteins that bind to special receptor sites on adjacent neurons. They bridge synapses. 1. Acetylcholine: most common type - used in

brain and in transmission to muscles. 2. Norepinephrine (noradrenaline): Function in the CNS and Autonomic nervous system - inter neuron communication. 3. Dopamine and seratonin: Related neurotransmitters in brain - involved in sleep, moods, attention, and learning. Dopamine inhibits pain. 4. GABA (gamma aminobutyric acid)

Acts inhibitory in the synapse - prevent transmission of message across synapse. 5. Gasses: Mostly NO and CO. NO acts to relax smooth muscle around blood vessels thus causing them to dilate (ex. Heart, penis). Nitroglycerine, viagra

Organization of the NERVOUS SYSTEM CNS spinal cord brain PNS cranial nerves

spinal nerves sensory fibers SOMATIC NERVOUS SYSTEM SKELETAL MUSCLES motor fibers AUTOMOMIC


The Central Nervous System Includes the brain and spinal cord. cord Highly protected by bone meninges and bathed in cerebro-spinal fluid Gray matter within the CNS does not contain myelin while white matter

is surrounded by fatty myelin. myelin Main Regions of the BRAIN 1. Cerebrum - largest portion of the brain consisting of 2 hemispheres with many folds (cerebral cortex / conscious thought) 2. Diencephelon - consisting of the hypothalmus,

thalmus and pineal and pituitary glands ( homeostasis) 3. Cerebellum - below the cerebrum at the back of the brain ( receives sensory input from the joints and muscles / responsible for voluntary muscle contractions) 4. Brain Stem - consisting of the midbrain, pons and medulla oblongata ( breathing rate and heart rate) The Brain

The Brain The Medulla part of the brain stem just above the spinal cord Controls breathing and heart rate Responsible for involuntary actions Cerebellum

Co-ordinates all motor functions Receives sensory input from joints and muscles. Takes muscle commands from the cerebrum and ensures that all related muscles contract in the correct sequence. Also involved in learning and remembering motor responses. Thalamus All sensory nerves go through the thalamus

It acts as a filter for the higher brain often referred to as the GATE KEEPER Once the higher brain is aware of a stimulus, the thalamus will filter it out if it is not significant to the higher brain. Hypothalamus It contains centers for controlling most basic body needs; thirst, thirst hunger,

hunger etc. Also can trigger some very basic behaviors: behaviors rage, rage fear, fear sexual behavior, behavior and pleasure. pleasure This part of the hypothalamus is referred to as the Limbic System.

System The hypothalamus, along with the pineal gland, gland also determine our circadian rhythms. rhythms The Pituitary Gland Called the Master Gland as its hormone control most other glands (termed tropic hormones).

Contains two parts: 1. The posterior Pituitary Stores and releases hormones produced in the hypothalamus. hypothalamus 2.The Anterior Pituitary Makes and releases its own hormones. Releases them upon

stimulation from hypothalamus Hormones include: Growth hormones, Prolactin (causes lactation), FSH and LH (reproductive), and ACTH (stimulates release of adrenalin).

Hormones of Posterior Pituitary are: A. Oxytocin: causes contraction of selected smooth muscles (uterus and milk ducts). ducts B. ADH: effects the kidneys and allows the body to conserve water (more concentrated urine). urine

The Cerebrum Largest part of the brain higher brain controls voluntary actions and our conscious thoughts Many folds in the outer cortex gray matter increases the surface area The RIGHT and LEFT HEMISPHERES of the brain are connected by the CORPUS CALLOSUM which is a network of nerve fibers. Your right side of the brain controls the left side of your body and visa versa.

Lobes of the Cerebrum 1. Frontal Lobe: Lobe motor area, concentration, planning, judgment, problem solving. 2. Parietal Lobe: Sensory for touch and taste, speech and language centers. 3. Temporal Lobe: Sensory for

hearing and smell, memory and sensory interpretation. 4. Occipital Lobe: Vision and integration of vision with other senses. LIMBIC SYSTEM In mammals, the ARAS ascending reticular activating system is composed nerve fibers that connect the spinal cord and the brain. LIMBIC

SYSTEM consists of the hippocampus, hippocampus olfactory cortex, cortex and the amygdala. HIPPOCAMPUS is responsible for memory and learning. AMYGDALA mediates basic emotions (fear, anger), involved in anger, anger defensiveness,

defensiveness and fear, also emotional bonding, bonding and is involved in recognizing the emotional content of facial expression. expression Memory and Learning Our memories are stored in various places in our Memory and

Learning. Short-term memory stored in the frontal lobes. The establishment of long-term memory involves the hippocampus. hippocampus The transfer of information from short-term to long-term memory. Is enhanced by repetition (remember that when you are preparing for an exam). Influenced by emotional states mediated by the amygdala.

amygdala Influenced by association with previously stored information. Brain activity is measured in (alpha and beta waves) electroencephalograph machine EEG EEG Different types of long-term memories are stored in different regions of the brain. Memorization-type memory can be rapid.

Primarily involves changes in the strength of existing nerve connections. Learning of skills and procedures is slower. Appears to involves cellular mechanisms similar to those involved in brain growth and development. The Brain We also know that the more a memory trace is used, the easier it is to use it later

(practice makes perfect). Not enough neurons (10 billion) to store all memories inside them. Stored in synapses? Each neuron has about 1000 synapses with other neurons. Still not enough possible connections. shirt fly

open me shout exit book cat

door juice mouse out dog in say

bed tree ball home bird grass

boy doll sad ring Lateralization of Brain Function. The left hemisphere. Specializes in language, math, logic operations, and the

processing of serial sequences of information, and visual and auditory details. Specializes in detailed activities required for motor control. The right hemisphere. Specializes in pattern recognition, spatial relationships, nonverbal ideation, emotional processing, and the parallel processing of information.

The Peripheral Nervous System Contains two divisions: 1. Somatic 2. Automomic SOMATIC nervous system is made of spinal and cranial nerves connecting directly to CNS and controls all voluntary actions. Ganglion are sensory neuron

cell bodies which lie outside the vertebrae and connect sensory neurons to inter neurons. Cranial Nerves: Nerves 12 pairs come directly off the brain. Some are sensory only (optic, auditory) rest are mixed.

Control head and upper neck. Includes Vagus nerve, that forms part of the autonomic nervous system responsible for breathing rate. Organization The Spinal Cord The Reflex Arc: Used to respond to emergencies.

Three types of neurons involved: Sensory neurons: from sensory receptor to spinal cord. Motor neurons: connect spinal cord to muscles.

Interneurons: inside spinal cord, connect sensory neuron to motor neuron. Used as brain bypass when response is obvious. Important to prevent injuries.

Autonomic Nervous System Made of two opposing divisions: The Sympathetic Division: Derived from nerves which connect to a ganglionic chain from the thoracic and lumbar regions of the spinal cord. cord Is stimulatory to most organs (heart, breathing, blood pressure, pupils) but inhibitory to digestive system (parasympathetic)

Prepares body for action fight or flight The Parasympathetic Division: Derived from nerves which connect to a ganglionic chain from the cranial and sacral regions of the spinal cord. It is inhibitory to most organs (heart, breathing, blood pressure, pupils) but stimulates digestive and reproductive systems. Used during rest and is antagonistic to sympathetic

system and returns systems to normalcy DRUG ADDICTIONS

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