Nervous System. All behavior ultimately has its roots in the biology of the nervous system

Transcription

1 Nervous System All behavior ultimately has its roots in the biology of the nervous system

2 Cells in the Nervous System

3 The Neuron - Microanatomy Neurons are the building blocks of the nervous system There are approximately 100 billion of them in the nervous system All neurons have the same basic structures Cell body (contains all of the DNA and controls cellular functions) Axon (take information away from the cell body) Some neurons can be up to 3 or 4 feet long Myelin sheathing around fiber helps to increase speed of conduction (up to 10X the speed, protects the fiber, is found in vertebrate animals, and is a fat that is critical in the health of the nervous system Dendrites (take information to the cell body about connections per neuron!) Synapse is the end point of the neuron and is where one neuron communicates with another We are born with all of the neurons we will ever have There is a thinning of neurons some time during adolescence Sometimes functions lost by some neurons are taken over by other neurons, this is called plasticity

4 Typical Neuron

5 Typical Neurons

6 Microphysiology The Action Potential Neurons are filled with and surrounded by fluids Fluids contain ions (electrolytes) which are Na+, K+, and Cl There are relatively more Na+ outside than inside the neuron giving the inside a negative charge (-70mv). This is called the resting potential. The charge within the neuron changes when it is stimulated to fire. This occurs because the membrane opens up. The inside of the neuron is momentarily more positive than the outside (1/1000 second) and it goes up to +40mv. This is called depolarization. The membrane closes quickly and this is followed by a period when the neuron cannot fire called the refractory period when K+ is being pumped out of the neuron. Eventually, the Na+/K+ pump re-establishes the resting potential. It is said that this process is all or none. The process of the action potential is the same in all neurons in the body and occurs between 200 and 1000 times per second! Levels of electrolytes in the body can affect the functioning of the nervous system.

7 Action Potential - Exchange of Ions

8 The Action Potential

9 Propagation of Action Potential

10 Macrophysiology Communications between neurons in the synapse When the impulse of the action potential reaches the synapse on the pre-synaptic side, the membrane in the synapse opens and neurotransmitters are released which stimulate the adjacent membrane, the post-synaptic membrane, to open and another action potential to occur. Neurotransmitters are amino acids or proteins that are much bigger than the ions within the cells and find specific receptor sites on the post-synaptic membrane. Neurotransmitters can either excite or inhibit the postsynaptic membrane. Diet can affect the amount of neurotransmitters in the nervous system.

11 The Synapse

12 Acetylcholine Memory (Alzheimer s Disease) Neuromuscular Junction Poisoning Neurotransmitters Black Widow Spiders excess production Botulism/Curare blocks release Norepinephrine Arousal/anxiety Depression Dopamine Mood Movement/Parkinson s Disease/tremors (too much) Serotonin Mood Schizophrenic symptoms Endorphins Pain mediation Natural mechanism within the body

13 More Neurotransmitters Ananamide Marijuana like neurotransmitter Runner s high GABA (Gamma Amino Butyric Acid) Most abundant inhibitory neurotransmitter Glutamine Most abundant excitatory neurotransmitter Vasopressin Oxytocin Regulates levels of fluids in the body Regulates the production/release of milk NMDA (n-methyl, d-aspartate) Secondary release causes structural and functional changes in the synapse

14 Neurotransmitters

15 The Big Picture of the Nervous System

16 The Big Picture Central Nervous System Brain Hind Brain (vegetative functions) Mid Brain (homeostatic functions) Forebrain (higher mental functions) Spinal Cord Transmission of impulses up/down the spinal cord Reflex arc Peripheral Nervous System Autonomic Nervous System Fight/Flight Response Sympathetic arousal (+) Parasympathetic arousal (-) Endocrine System Production and release of hormones (like NT) into the blood stream Somatic Nervous System Sensory (afferent) transmission Motor (efferent) transmission

17 Autonomic Nervous System

18 Endocrine Glands Hypothalamus (Stimulates release of hormones by pituitary gland) Pituitary Gland (anterior and posterior pituitary) Master gland (controls other endocrine glands) Growth Hormone Regulates water retention in kidneys Release of milk after childbirth Thyroid Gland Thyroxin regulates the rate of oxygen consumption Hyperthyroidism/hypothyroidism Parathyroid Use of calcium and potassium in body Adrenal Glands Production of adrenaline/epinephrine during stress Immune system response Production of sex hormones Pancreas Production of Insulin (absorption of glucose into cells) and glucagon (storage of glucose as glycogen) Gonads Testosterone in men (secondary sex characteristics) Estrogen/Progesterone in women (secondary sex characteristics) Pineal Gland Melatonin which regulates sleep

19 The Endocrine System

20 Anabolic Steroids

21 Spinal Cord Hidden within the spinal column for protection Allows for the transmission of impulses to and from the brain Sensory impulses leave the spinal column on the back (dorsal) area of the spinal cord Motor impulses return on the front (ventral) area of the spinal cord Gray area in the center (butterfly shaped area) are the cell bodies while the white areas are myelin on axons Damage to the spinal cord can affect function from the point of injury downward called paralysis Damage to lower areas of the spinal cord cause paraplegia Damage to higher areas of the spinal cord cause quadriplegia Damage to one side (front, back, or side) of the spinal cord cause a hemiplegia Spinal reflexes The connection of sensory and motor roots by an interneuron allows for the quick response of the nervous system to avoid further damage to the body. Patellar and ulnar reflexes are examples of spinal reflexes Developmental reflexes

22 Spinal Column

23 Spinal Cord

24 The Reflex Arc

25 Hindbrain (lower center) Vegetative functions like breathing, heart rate, blood pressure, and some auditory & visual reflexes The brain stem is composed of the Medulla Oblongata which is involved in involuntary reflexes including tongue and eye movements, swallowing, heart rate, respiration, swallowing, startle response, ability to sleep, sense of balance (vestibular function) Cross laterality exists within the medulla oblongata Pons is the relay station for messages going to and from the brain Responsible for rapid eye movement during sleep Cerebellum smoothes and coordinates body movements Especially responsible for complex, repetitive movements Balance and equilibrium Damage results in jerky tremors, involuntary trembling, walking, vertigo, slurred speech (scanning speech), dyspraxia Reticular Activating System (RAS) is at the top of the brain stem and is responsible for activation and arousal Acts as a valve for sensory messages from lower to higher centers of the brain

26 Midbrain Limbic System controls instinctive, complex behaviors Involved in the display of emotion Amygdala produces reactions of rage and aggression when stimulated Septum reduces the intensive of emotional reactions when stimulated Hippocampus is involved in the formation of long term memories Hypothalamus mediates motivational and emotional behaviors and homeostatic functions like eating, thirst, warming of the body, and sexual behavior. Basal Ganglia is a collection of structures that controls slow body movements Thalamus is a relay station between the cerebral cortex and the lower areas of the brain. Integrates sensory messages and sends them to the cerebral cortex and is involved in wake-sleep patterns.

27 The Core of the Brain

28 Limbic System

29 More Limbic System Another view

30 Emotions and Memory

31 Forebrain (cerebral cortex) Large outer covering of the brain involved in higher mental functions and voluntary action Two hemispheres (right/left) Each hemisphere is connected by the corpus callosum Four Lobes with one in each hemisphere Frontal Temporal Occipital Parietal

32 The Cerebrum

33 Cerebral Layers

34 Cerebral Complexity

35 The Cerebral Cortex

36 Frontal Lobes Consciousness Initiating activity Judgment Inhibition of emotional responses Expressive language Broca s Aphasia (expressive aphasia) Assigns meaning to words Word associations Motor strip (motor homunculus) Personality

37 Speech Centers

38 The Homunculus Motor and Sensory Strips

39 Gateway to Consciousness

40 Frontal Lobe Problems Paralysis Sequential movement Loss of spontaneity Loss of flexibility of thinking Perseveration Inattention Change in social behavior Changes in personality Difficulties with problem solving Broca s Aphasia

41 Temporal Lobes Hearing ability Memory (short & long term) Musical ability Some visual perception Categorizing objects Temporal Lobe Epilepsy

42 Temporal Lobe Problems Difficulty with faces (prosopagnosia) Difficulty understanding spoken words (Wernicke s Aphasia) Disturbance with selective attention to what we see and hear Difficulty with identification of and verbalization about objects Loss of short term memory Increase or decrease in sexual behavior Kluver-Bucy Syndrome Inability to categorize things Persistent talking with right lobe damage Increase in aggressive behavior Kluver-Bucy Syndrome

43 Vision Occipital Lobes Primary association area (direct response to visual stimuli) Secondary association area (gives meaning to those visual stimuli)

44 Visual Pathways

45 Occipital Lobe Problems Defects in vision (visual field cuts) Difficulty locating objects Difficulty identifying colors (color agnosia) Visual hallucinations Visual illusions Word blindness (difficulty recognizing words) Difficulty recognizing drawn objects Difficulty identifying movements (movement agnosia) Difficulty reading and writing

46 Parietal Lobes Visual attention Touch perception (somatosensory homunculus) Goal directed voluntary movements Manipulation of objects Integration of different senses that allows for understanding a single concept (association cortex)

47 The Homunculus Motor and Sensory Strips

48 Parietal Lobe Problems Problems attending to more than one thing at a time Difficulty naming objects (dysnomia) Difficulty locating words for writing (dysgraphia) Difficulty reading (dyslexia) Difficulty with drawing objects (constructional dyspraxia) Difficulty distinguishing left from right Difficulty doing math (dyscalculia) Lack of awareness of certain body parts and/or surrounding space (dyspraxia) that lead to difficulty in self-care (right side neglect) Difficulty focusing visual attention Difficulty with eye/hand coordination

49 Hemisphere Differences Each hemisphere has specific functions Left usually dominant and is involved in speech & language Right usually involved in expression and interpretation of emotion and processing visualspatial (artistic) information

50 Hemisphere Differences

51 Imaging Techniques The last three decades has seen a tremendous advance in noninvasive diagnostic techniques EEG was used since the 1940 s but has limited use and limited advantages X-ray techniques are also limited to examination of bony structures of the skull CAT (computerized axial tomography) allows for the investigation of brain in two dimensions MRI (magnetic resonance imaging) utilizes large external magnets to provide a rich three dimensional image of the brain fmri (functional magnetic resonance imaging) allows for the investigation of the brain while engaged in activity PET (positron emission tomography) uses irradiated glucose to investigate the metabolism of brain tissue under specific conditions

52 MRI

53 PET Scan