The Nervous System Characteristics of life All organisms

The Nervous System Characteristics of life All organisms

The Nervous System Characteristics of life All organisms carry out the same functions of life: 1) All life is made of cells. 2)

Homeostasis: maintain constant conditions. 3) Reproduction: life comes from life (biogenesis). 4) Heredity directed by DNA for growth & development. 5) Metabolism: energy utilization and

transformation. 6) Response to stimuli: organisms sense and react to their environment. Maintain constant internal body conditions Examples of homeostasis: Osmosis & diffusion remove wastes from single cells. Birds and mammals regulate body

temperature. Guard cells control water loss in leaves. Maintain constant internal body conditions Requirements for homeostasis: Ability to sense when changes have occurred in the internal and external environment. Ability to respond with appropriate adjustments.

Phototrophism a plant senses and grows toward the sun The mammalian nervous system The nervous system consists of the central nervous system (CNS) and peripheral nervous system (PNS). CNS = brain & spinal cord Organization of the nervous system The brains anatomy

Conscious thought resides in the forebrain. Reflexes & voluntary movement are controlled by the midbrain. Vital body functions & coordination are controlled by the hindbrain. Front Organization of the nervous system The brains anatomy: the forebrain The cerebrum is for conscious thought.

Two hemispheres manage different tasks. The corpus callosum connects the two halves of the brain. Crossover in the corpus callosum causes the left hemisphere to manage the right side of the body. Organization of the nervous system The brains anatomy: the forebrain In the cerebrum, nerve connections create memories.

Cerebral cortex: the outer surface (gray matter) where infor-mation processing occurs is composed of nerve cell bodies. White matter consists of the connecting cables of nerve cells (the axons). The many folds increase surface area = more nerve cells. Organization of the nervous system The brains anatomy: the forebrain The cerebral cortex is divided into 4 sections

called lobes. Frontal Lobe - reasoning, planning, parts of speech, move- ment, emotions, and problem solving. Parietal Lobe - movement, orientation, recognition, and perception of stimuli. Occipital Lobe - visual processing. Temporal Lobe perception and recognition of sounds, memory, speech.

Organization of the nervous system The brains anatomy: the forebrain The hypothalamus controls the autonomic nervous system. It synthesizes and secretes hormones that stimulate or inhibit the secretion of pituitary hormones, which then control body tem- perature, hunger, thirst, fatigue, sleep, and circadian cycles (like menstruation). Above the hypothalamus lies the thalamus, a major clearinghouse for information going to and from

the spinal cord and the cerebrum. Organization of the nervous system The brains anatomy: the midbrain The uppermost part of the brain stem; relays information associated with vision, hearing, motor control, sleeping & waking, arousal (alertness), and temperature regulation.

Organization of the nervous system The brains anatomy: the hindbrain Composed of the pons, medulla oblongata, and cerebellum. The oldest part of the human brain. The cerebellum is for balance. (Remember: humans are bipedal.) Organization of the nervous system The brains evolution The human brain has a large

cerebrum with many folds increase surface area. to Brains of primates (also note the cerebellum) Organization of the nervous system The PNS transmits information to and from the CNS and regulates movement and internal environment

The somatic nervous system carries signals to skeletal muscles. * The autonomic nervous system regulates the internal *soma *soma = = body: body: environment, in an involuntary manner chromosome chromosome (homeostasis).

liposome liposome Conduction of nerve impulses Nerve impulses are conducted from receptors to the CNS by sensory neurons, within the CNS by relay neurons, and from the CNS to effectors by motor neurons. Conduction of nerve impulses

Organization of the nervous system The nervous system is composed of cells called neurons that carry rapid electrical impulses. Draw and label: Conduction of nerve impulses Nerve impulse passing along a nonmyelinated neuron. Myelin sheath speeds depolarizations, which can only occur at the nodes of Ranvier. In multiple sclerosis the sheath degenerates, and

muscles dont respond to desires. Conduction of nerve impulses Nerve impulse passing along a nonmyelinated neuron. Conduction of nerve impulses In an electrical synapse, current flows directly from one cell to another via

a gap junction. Conduction of nerve impulses The vast majority of synapses are chemical synapses. Post-synaptic cell Pre-synaptic cell ++ ions to enter the pre-synaptic cell.

1) 1) The The action action potential potential causes causes Ca Ca++ ions to enter the pre-synaptic cell. 2) 2) Vesicles Vesicles of of neurotransmitter

neurotransmitter leave leave the the cell cell by by exocytosis. exocytosis. 3) 3) Neurotransmitter Neurotransmitter diffuses diffuses to to post-synaptic post-synaptic cell.

cell. + + 4) 4) Neurotransmitter Neurotransmitter opens opens Na Na channels channels to to propagate propagate a a new

new action action pote pote 5) 5) Neurotransmitter Neurotransmitter is is reabsorbed reabsorbed by by pre-synaptic pre-synaptic cell. cell.

The Endocrine System Response to stimuli Internal sensory nerves send signals to the hypothalamus. The hypothalamus monitors body chemistry. It reacts to changes and responds by sending chemical signals to endocrine glands. Hormones are the mes-

chemical sengers. The endocrine system Homeostasis in humans involves maintaining blood & tissue fluid (pH, CO2 concentration, sugar levels, body temper-ature, and water balance) between certain limits: Levels of variables are corrected by negative feedback (hormones are released until the stimulation is removed).

The endocrine system The endocrine system consists of glands that release hormones that are transported in the blood. The endocrine system Animal hormones are chemical signals that are secreted into the circulatory system and communicate regulatory messages within the body. Hormones reach all parts the body, but only

cells are respond. Receptor in: of target equipped to cell membrane nucleus

Thermoregulation The hypothalamus monitors body heat. Thermoregulation The control of body temperature involves physiological and behavioral adjustments that balance heat gain and loss. Most biochemical and physiological processes are very sensitive to changes in body temperature; enzymes are damaged.

Thermoregulation Humans are endotherms; blood transfers metabolic heat throughout the body. The hypothalamus monitors body heat and sends out hormones that make skin arterioles constrict, cause us to shiver or perspire, increase metabolism, or produce discomfort so we change clothes, etc. As As a a result

result mammals mammals need need more more food food than than reptiles. reptiles. Thermoregulation

Skin Skin arterioles arterioles The human body is adapted to avoid overheating (or getting chilled): Upright posture Sweat glands Lack of hair Dehydration Dehydration a lack of water (our skin is not

water-tight like that of a reptile; cells lose water AND we perspire). Water serves many purposes within the body. Dehydration Dehydration a lack of water (our skin is not water-tight like that of a reptile; cells lose water AND we perspire). Typically we need 2 liters of water per day; more in hot, dry weather or with heavy exertion.

Dehydration Dehydration Severe dehydration causes stroke, which can be short time. heat deadly in a Control of blood glucose Not only does the pancreas produce digestive

enzymes, it secretes hormones that maintain glucose homeostasis. Acinar cells (exocrine system) secrete digestive enzymes. Islets of Langerhans secrete the hormones insulin and glucagon. Control of blood glucose Insulin and glucagon are antagonistic hormones that help maintain glucose homeostasis. Glucagon (produced by alpha cells) increases blood

glucose levels: Stimulates conversion of glycogen to glucose in the liver Stimulates breakdown of fat and protein into glucose. Control of blood glucose Insulin and glucagon are antagonistic hormones that help maintain glucose homeostasis. Insulin (produced by beta cells) reduces blood glucose levels:

Promotes the cellular uptake of glucose Slows glycogen breakdown in the liver and promotes fat storage Control of blood glucose Know how insulin glucagon baleach other. and ance

Diabetes Diabetes mellitus is caused by a deficiency of insulin or a decreased response to insulin in target tissues. It is marked by elevated blood glucose levels. Type I diabetes is an autoimmune disorder in which the immune system destroys pancreatic beta cells . Type II diabetes involves insulin deficiency or reduced response

of target cells due to change in insulin receptors. Diabetes Type 1 diabetes Usually starts in childhood and accounts for 5 - 10% of all diagnosed cases of diabetes. People with type 1 diabetes produce little or no insulin and must use insulin daily to control their condition. Injection sites

Diabetes Type 2 diabetes Usually starts in adulthood, but it is being diagnosed more often in children because of greater childhood obesity. It accounts for 90 - 95% of cases. People with type 2 diabetes are resistant to the insulin the body makes. It is controlled with diet and exercise, and sometimes oral drugs or insulin.

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