Nerves Nerves consist of neural “cables” containing many axons. They are part of the peripheral nervous system and connect muscles, glands, and sense organs to the central nervous system.
Peripheral Nervous System Links the CNS to the organs, muscles, and glands of the body. Sensory receptors receive sensory information. The PNS transmits that information along sensory nerves to the CNS Motor neurons transmit commands to effectors (muscles and glands)
Peripheral Nervous System PNS has two parts Somatic or Somatosensory (SNS): nerves controlling voluntary movement and control of skeletal muscles and receiving sensory information Autonomic (ANS): controls (self-regulated) activity of glands, organs, blood vessels, heartbeat, digestion Sympathetic Parasympathetic
Sympathetic and Parasympathetic Sympathetic Nervous System Accelerates heartbeat Raises B.P. and blood sugar Slows digestion Increases respiration and perspiration Dilates pupils Stimulates secretion of epinephrine and norepinephrine Diverts blood flow away from reproductive organs Relaxes bladder Parasympathetic Slows heartbeat Lowers blood sugar Contracts pupil Stimulates digestion, gall bladder Contracts bladder Allows blood flow to sex organs
Sympathetic and Parasympathetic Sympathetic Nervous System (Arousing) Fight or Flight. In situations of high stress (survival-wise), expends energy, increases alertness and readiness by diverting blood/nutrients from non-essential functions to functions that will increase chance of immediate survival Parasympathetic Nervous System (Calming) When stress subsides/threat is no longer present, undoes the effects of the sympathetic nervous system Calms and conserves energy, returning to routine maintenance so that life can go on.
Sympathetic/Parasympathetic Stress is present Stress has subsided
Somatic Nervous system Includes all neurons connected with muscle, skin, or sensory organs 12 pairs of cranial nerves (connect brain to periphery) Transmit sensory info about smell, taste, vision, balance, and general sensation in the head to the brain and transmit signals from the brain to motor neurons that are involved in movements of the face and throat 31 Pairs of Spinal Nerves (connect spine to periphery) Transmit sensory info from body to brain and transmit signals to innervate motor neurons that control skeletal muscle Each spinal nerve has a ventral root and a dorsal root.
Spinal Nerve “Mixed” because it contains both motor neurons and sensory neurons Arrows are the direction the stimulus is traveling Ganglion=mass of nerve tissue containing cell bodies In the CNS these are called nuclei
Autonomic Nervous System Sensory and motor neurons Motor neurons that control smooth muscle or cardiac muscle Also differs from somatic nervous system in that it uses two sets of motor neurons instead of one
Autonomic Nerves Preganglionic neurons arise in CNS and run to a ganglion in the body where they synapse with postganglionic nerves. Postganglionic neurons run to the effector organ (cardiac muscle, smooth muscle, or gland)
Sympathetic Nervous System The preganglionic neurons of the sympathetic nervous system arise in the spinal cord and pass into the sympathetic ganglia. These ganglia are organized into two chains that run parallel to and on either side of the spinal cord. In the sympathetic ganglia, the preganglionic neurons can pass up and down the chain of sympathetic ganglia to synapse with postganglionic neurons in a higher or lower ganglion. These postganglionic neurons then synapse with effectors or they can reenter the spinal nerve and ultimately pass out again later on. This enables communication of information to the different organs that are effected by sympathetic arousal
Sympathetic Nervous System The preganglionic neuron uses Ach as its NT to stimulate action potential in the postganglionic neuron. The effect is always excitatory The postganglionic neuron uses norepinephrine as its NT where it synapses with effectors. The effect is excitatory or inhibitory depending on the receptor at each synapse
Parasympathetic Nervous System Main nerves are the tenth pair of cranial nerves (the Vagus nerves). They originate in the Medulla Preganglionic parasympathetic neurons also arise from other areas of the brain and the lower tip of the spinal cord. These synapse with postganglionic neurons which are located near or on effecter organs. Ach is the NT a most of these synapses
The Endocrine System Hormones have to travel through the blood stream to target organs. Compared to neurotransmitters, they take longer to act (several seconds compared to fractions of a second) but the effect is also longer lasting The endocrine system and nervous system work together. Example: Adrenal gland and sympathetic nervous system, the pituitary gland and hypothalamus The body’s “slow” chemical communication system. Communication is carried out by hormones.
Hormones Chemical messengers that are synthesized and stored in glands of the endocrine system. When secreted, the travel through the blood stream and affect other tissues, including the brain. Influence growth, reproduction, mood, metabolism, sex, aggression Examples: Epinephrine (adrenaline), insulin, growth hormone, estrogen, testosterone
The Endocrine System Adrenal Glands Pituitary Glands Hypothalamus Parathyroids Testis/ovary Thyroid gland Pancreas
The Pituitary Gland Called the “Master Gland” because it releases hormones that tell other endocrine glands to release hormones. But the pituitary gland is controlled by the Hypothalamus. Also releases hormones that influence growth
Hypothalamus Releases hormones that stimulate or inhibit the pituitary gland. Also helps control body temperature, hunger, thirst, sleep- wake cycle, maintaining homeostasis
Adrenal Glands On top of the kidneys Release epinephrine and norepinephrine (adrenaline and noradrenaline) to produce “fight or flight” response under stressful situations Regulate salt and carbohydrate metabolism
Gonads Ovaries/Testes – Secrete male or female sex hormones. Regulate body development and maintain reproductive organs
Thyroid and Parathyroid Regulate metabolism, growth rate, and calcium levels
Pancreas Secretes Insulin to regulate blood sugar levels
Central nervous system Brain ~2% of body weight, uses ~20% of resources Composed of bunches of neurons, which form nerves Spinal cord Complex tangle of nerves that stretch from brain to tailbone Collects & transmits info between brain and peripheral nervous system Also initiates reflexes: automatic responses to an event
Simple Spinal Reflexes Reflex – Automatic response to stimuli Simplest reflex pathway is a single sensory neuron and a single motor neuron, often communicating through an interneuron Knee-jerk response, pain reflex, later you will learn about reflexes that we display only during certain periods of infancy. What purpose can you see in having actions that don’t require conscious processing?
Complex Neural Networks Interconnected neurons form networks in the brain. The brain learns by modifying these connections in response to feedback (inputs)
The Brain Three important parts Brain Stem (including the cerebellum and thalamus) –Midbrain and Hindbrain Limbic System - Forebrain Cerebral Cortex - Forebrain
Older Brain Structures/Lower Level Functions Brainstem Medulla Pons Reticular formation (passes through both brainstem and thalamus) Thalamus (extends from top of brainstem) Cerebellum (extends from rear of brainstem) Limbic system Amygdala Hypothalamus Hippocampus
Brainstem Automatic survival functions that occur without conscious effort Region of the brain where the spinal cord enters the skull; an extension of the spinal cord Crossover point where most nerves to and from each side of the brain connect with body’s opposite side
Brainstem Medulla - Regulates heart rate, breathing, blood pressure and has pathway for motor movement Pons – Helps coordinate movement Reticular Formation – Nerve network that controls Sleep and arousal, (Moruzzi & Magoun, 1961)
Brainstem Thalamus Sits at the top of the brainstem Receives sensory input(except smell)and directs them to sensory areas in the cortex then transmits replies to cerebellum and medulla Cerebellum – “Little Brain” Nonverbal learning and memory, Coordinates voluntary movement and balance Controls Learned/skilled movements that are automatic (i.e., walking)
Limbic System Memory, emotions, basic drives Hypothalamus Maintenance functions - Hunger, thirst, body temp., reproductive behavior Helps govern endocrine system Emotion and “Reward Center” (Olds & Milner (1954)) Hippocampus Processes memory (H.M., amnesia) Amygdala Aggression, fear, and perception of them Processing/encoding emotional memories Regulating feeding
Question? The limbic system is involved in controlling basic drives important for our survival as a species, feeding and reproducing. But it is also instrumental to the experience of fear and aggression. What do you make of the fact that these two particular emotions (unlike say, happiness or melancholy) are controlled by the same system that helps ensure our survival? What does Memory have to do with this?
Cerebral Cortex Intricate fabric of interconnected neural cells that covers the cerebral hemispheres Ultimate control and information processing structure Higher Functions/Newer neural networks 85% of brain weight, billions of nerve cells and 9 times as many glial cells Filled mainly with axons connecting the cortex to other brain regions Neural networks form specialized teams
Cerebral Cortex Glial Cells Provide nutrients to the neuron (Astrocytes) and myelin to insulate(oligodendrocytes and Schwann cells Guide neural connections Mop up ions and neurotransmitters May play a role in learning, thinking, information transmission and memory
Cerebral Cortex Two halves, four lobes, separated by Fissures Frontal lobe Motor cortex Parietal lobe Sensory cortex Body position Temporal lobe Auditory areas Occipital lobe Visual areas
Two Cerebral Hemispheres Contralateral arrangement – the left hemisphere receives inputs from and controls the right side of the body and vice versa Work together on many functions but can also simultaneously carry out different functions with minimal duplication of effort Corpus callosum Thick band of nerve fibers connecting the hemispheres and allowing them to communicate with each other
Functions of the Cortex The Motor Cortex is the area at the rear of the frontal lobes that control voluntary movements. The cortex of each hemisphere controls the opposite side of the body The Somatosensory cortex in the parietal lobes, receives information from skin surface and sense organs.
Motor and Sensory Cortex The body areas requiring precise control occupy the most cortical space on the Motor Cortex The more sensitive the body region, the larger the sensory cortex area devoted to it.
Functions of the Cortex Visual Cortex – In the Occipital Lobe Receives visual info from the eyes Auditory Cortex In the temporal lobes Receives auditory information from the ears
Association Areas of the Cortex The ¾ of the cortex, across all four lobes not devoted to sensory or muscle activity. Interpret, integrate information processed by the sensory areas, link sensory inputs with stored memories In the frontal lobes enable judgment, planning, processing memories, inhibitions, and personality In parietal lobes, enable mathematical and spatial reasoning In right temporal, enable facial Recognition.
Association Areas More intelligent animals have increased “uncommitted” or association areas of the cortex.
Specialization and Integration Complex human behaviors involve multiple specialized areas and association areas working together.
The Brain’s Plasticity Plasticity occurs during normal brain development but it is also the brain’s ability to modify itself after injury or loss of function Phantom limb Enhanced peripheral vision in deaf people The brain is sculpted by our genes and by a person’s environment and experiences Neural tissue reorganizes and in some cases regenerates (neurogenesis)
Split Brain Patients http://www.youtube.com /watch?v=aCv4K5aStdU With the corpus callosum severed, objects (apple) presented in the right visual field can be named. Objects (pencil) in the left visual field cannot.
Divided Consciousness The Right hemisphere is nonverbal but it can still make itself understood
Hemispheric Specialization Left brain Good with literal interpretations of language More active when a person is deliberating More “rational” Right Brain Making inferences about words and modulating speech to convey meaning Orchestrates sense of self Better with quick, intuitive responses Perceives objects better More involved in emotion, spatial reasoning
Hemispheric Specialization After damage to the right hemisphere, some patients exhibit indifference to the left side of their world – “hemi- neglect” The neglect can be multimodal, affecting auditory, visual, somatosensory Related to the right side’s involvement in spatial reasoning and sense of self. Damage to the left side does not have this effect.
Theories of lateralization – Why? May increase neural capacity Dominance by one side prevents the simultaneous initiation of incompatible responses/actions May increase capacity for parallel processing in the two hemispheres But then why do we display a consistent preference at the population level? Shouldn’t there be an equal ratio of left to right side preference?
Theories of Lateralization – How? Lateral birth position and neonatal head orientation preference are both predictors of handedness Lateral asymmetry in the uterine environment and maternal anatomy my lead to the left side of the uterus being more “favorable” for fetal positioning. But then why would we have any lefties at all?
Handedness Lefties are more likely than righties to process language with either the right hemisphere or with both hemisphere. 96% of righties process language primarily with left hemisphere. Left-handedness is more common among musicians, mathematicians, pro baseball players, architects and artists. Do you think there is a connection?
Handedness In the past, left-handedness was stigmatized in our society and as children, lefties were “trained” to use their right hands. In a world where most things are made for righties, lefties are More susceptible to accidental injury. On average, lefties live 9 years than people who are right- handed
Handedness Given these facts about left-handedness as well as what you have learned about research methods, what do you make of this graph?
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