The Brain
The brain is _____ lbs of tofo-like tissue containing ____ cells, including _____ neurons. On average, each neuron receives about ______ connections, called ______, from other neurons.
5lbs 1.1 trillion cells 100 billion neurons 5000 connections Synapses
Definition of Disease
Organ -> Defect -> Symptoms Femur -> Fracture -> Screaming, bleeding, deformity, disability
Neurons vs Other Cells Similarities with other cells:
Similarities with other cells: - Neurons and other body cells both contain a nucleus that holds genetic information. - Neurons and other body cells are surrounded by a membrane that protects the cell. - The cell bodies of both cell types contain organelles that support the life of the cell, including mitochondria, Golgi bodies, and cytoplasm.
Types of Neurons
-Sensory neurons carry information from the sensory receptor cells (sense organs, such as the eyes and ears) to the brain. -Motor neurons transmit information from the brain to the muscles of the body. Motor neurons control voluntary muscle activity such as speaking and carry messages from nerve cells in the brain to the muscles. -Interneurons are responsible for communicating information between different neurons in the body.
Each hemisphere is divided into 4 lobes: frontal, parietal, occipital and temporal.
1. FRONTAL LOBE - the frontal lobe of the forebrain is situated under the frontal bone of the skull and is located behind the forehead. The frontal lobe is important in controlling movement and in planning behavior. 2. PARIETAL LOBE - (the bone which lies between the frontal bone and the occipital bone of the skull). The parietal lobe of the forebrain is situated under the parietal bone of the skull and is concerned with controlling bodily sensations. 3. OCCIPITAL LOBE - the occipital lobe of the brain lies underneath the occipital bone of the skull, situated towards the back of the head. It is primarily devoted to controlling vision. 4. TEMPORAL LOBE -(the regions on either side of the head adjacent to the eyes). The temporal lobe of the forebrain is situated under the temporal bone of the skull and is concerned with the control of hearing. It also functions to enable us to recognize objects and faces.
Neurotransmitter
A chemical messenger that enables neurons to pass signals to each other and thus allow the body to function properly. Electrical signals are converted to chemical signals at the synapse. This is known as neurotransmission at a synapse. Neurotransmitters play an important role in the development of brain disorders and in their treatment. A neurotransmitter is a chemical messenger that carries, boosts, and modulates signals between neurons and other cells in the body. In most cases, a neurotransmitter is released from the axon terminal after an action potential has reached the synapse. The neurotransmitter then crosses the synaptic gap to reach the receptor site of the other cell or neuron. Then, in a process known as reuptake, the neurotransmitter attaches to the receptor site and is reabsorbed by the neuron. Neurotransmitters play a major role in everyday life and functioning. Scientists do not yet know exactly how many neurotransmitters exist, but more than 100 chemical messengers have been identified. When neurotransmitters are affected by disease or drugs, there can be a number of different adverse effects on the body. Diseases such as Alzheimer's and Parkinson's are associated with deficits in certain neurotransmitters.
Neuron
As it's receiving synapses, a neuron gets signals - usually as a burst of chemicals called neurotransmitters - from other neurons. Signals tell a neuron to either fire or not fire. Whether it fires depends mainly on the combination of signals it receives each moment. In turn, when a neuron fires, it sends signals to other neurons through its transmitting synapses, telling them to fire or not. A typical neuron fires 5-50 times per second.
Limbic (Emotional) Brain
CORTICAL (CONSCIOUS) • Prefrontal Cortex (PFC) • Orbitofrontal Cortex (OCC) • Anterior Cingulate Cortex (ACC) SUBCORTICAL (UNCONSCIOUS) • Midbrain • Ventral Tegmental Area (VTA) • Nucleus Accumbens (NA) • Hippocampus • Amygdala • Hypothalamus
Dendrite
Dendrites are treelike extensions at the beginning of a neuron that help increase the surface area of the cell body. These tiny protrusions receive information from other neurons and transmit electrical stimulation to the soma. Dendrites are also covered with synapses. Dendrite Characteristics Most neurons have many dendrites However, some neurons may have only one dendrite Short and highly branched Transmits information to the cell body
Neurons vs Other Cells Differences that make neurons unique:
Differences that make neurons unique: - Unlike other body cells, the majority of neurons are unable to undergo cell division or repair. This limitation results in irreversible damage to the nervous system after trauma, intoxication, oxygen deficiency or stroke. - Neurons have a membrane that is designed to sends information to other cells. The axon and dendrites are specialized structures designed to transmit and receive information. The connections between cells are known as a synapses. Neurons release chemicals known as neurotransmitters into these synapses to communicate with other neurons.
Prefrontal Cortex
Executive Functioning • Abstract thinking • Motivation for goal-directed activity • Planning and problem-solving • Attention to tasks • Inhibition of impulsive responses • Weighing consequences of future actions • Flexibility of responses (rule shifting) • Reflective decision-making Gives us the capacity to use past experience and knowledge to make sense of our current behavior Failure of Executive Functioning (damage to Prefrontal Cortex) • Premature, unduly risky, poorly conceived actions • Urgency • Sensation seeking • Expressed emotions inappropriate to the situation • Deficits in attention, lack of perseverence • Rapid responses without reflection or premeditation • Insensitivity to consequences • Impulsive choice (increased delay discounting)
Forebrain consists of:
Forebrain cerebral cortex prefrontal cortex cerebrum corpus callosum cingulate gyrus hypothalamus thalamus Forebrain - The anterior and largest portion of the brain; includes the cerebral hemispheres, the limbic system, the thalamus and hypothalamus, and the corpus callosum. Each of the hemispheres is divided into four lobes: frontal, parietal, occipital and temporal. Collectively, the forebrain functions to control cognitive, sensory and motor function, and regulate temperature, reproductive functions, eating, sleeping and the display of emotions.
Hindbrain consists of:
Hindbrain brainstem cerebellum medulla oblongata pons Hindbrain - The area of the brain comprising the pons, medulla and cerebellum. The hindbrain functions collectively to co-ordinate motor activity, posture, equilibrium and sleep patterns and regulate unconscious but essential functions, such as breathing and blood circulation.
Midbrain consists of:
Midbrain basal nuclei brainstem cerebral peduncle locus coeruleus tectum substantia innominata Midbrain - Positioned between the hindbrain and the forebrain, the midbrain forms part of the brainstem and connects the brainstem to the forebrain. The midbrain is responsible for controlling sensory processes.
Neuron - basic definition
Neurons are information messengers. They use electrical impulses and chemical signals to transmit information between different areas of the brain, and between the brain and the rest of the nervous system. Everything we think and feel and do would be impossible without the work of neurons and their support cells (the glial cells). Neurons use their highly specialised structure to both send and receive signals. Individual neurons receive information from thousands of other neurons, and in turn send information to thousands more. Information is passed from one neuron to another via neurotransmission. This is an indirect process that takes place in the area between the nerve ending (nerve terminal) and the next cell body. This area is called the synaptic cleft or synapse. Neurons are responsible for the transport and uptake of neurotransmitters - chemicals that relay information between brain cells. A neuron is a nerve cell that is the basic building block of the nervous system. Neurons are similar to other cells in the human body in a number of ways, but there is one key difference between neurons and other cells. Neurons are specialized to transmit information throughout the body. These highly specialized nerve cells are responsible for communicating information in both chemical and electrical forms. There are also several different types of neurons responsible for different tasks in the human body.
Neurons have 3 basic parts:
Neurons have three basic parts: a cell body and two extensions called an axon (5) and a dendrite (3). Within the cell body is a nucleus (2), which controls the cell's activities and contains the cell's genetic material. The axon looks like a long tail and transmits messages from the cell. Dendrites look like the branches of a tree and receive messages for the cell. Neurons communicate with each other by sending chemicals, called neurotransmitters, across a tiny space, called a synapse, between the axons and dendrites of adjacent neurons.
Prefrontal Cortex
Part of the cerebral frontal cortex which covers the front part of the frontal lobe. • The "Human" Brain • Processes judgment, executive decision making, executive decision making • Conscious emotions • Confers emotional meaning onto objects in the world • Seat of the Self and Personality • "Love, Morality, Decency, Responsibility, Spirituality" • Behavioral regulation • Reflective decision-making • Inhibition of socially inappropriate actions • Emotional and sensory integration • Planning complex behaviors • Personality expression
Axon Hillock
The axon hillock is located at the end of the soma and controls the firing of the neuron. If the total strength of the signal exceeds the threshold limit of the axon hillock, the structure will fire a signal (known as an action potential) down the axon.
Axon
The axon is the elongated fiber that extends from the cell body to the terminal endings and transmits the neural signal. The larger the axon, the faster it transmits information. Some axons are covered with a fatty substance called myelin that acts as an insulator. These myelinated axons transmit information much faster than other neurons. Axon Characteristics Most neurons have only one axon Transmit information away from the cell body May or may not have a myelin covering
The Brain
The central nervous system (CNS) consists of the brain and the spinal cord, immersed in the cerebrospinal fluid (CSF). Weighing about 3 pounds (1.4 kilograms), the brain consists of three main structures: the cerebrum, the cerebellum and the brainstem. Cerebrum - divided into two hemispheres (left and right), each consists of four lobes (frontal, parietal, occipital and temporal). The outer layer of the brain is known as the cerebral cortex or the 'grey matter'. It covers the nuclei deep within the cerebral hemisphere e.g. the basal ganglia; the structure called the thalamus, and the 'white matter', which consists mostly of myelinated axons. Cerebellum - responsible for psychomotor function, the cerebellum co-ordinates sensory input from the inner ear and the muscles to provide accurate control of position and movement. Brainstem - found at the base of the brain, it forms the link between the cerebral cortex, white matter and the spinal cord. The brainstem contributes to the control of breathing, sleep and circulation.
CNS
The central nervous system (which includes the brain and spinal cord) is made up of two basic types of cells: neurons (1) and glia (4) & (6). Glia outnumber neurons in some parts of the brain, but neurons are the key players in the brain
Forebrain
The forebrain is the largest part of the brain, most of which is made up of the cerebrum. Other important structures found in the forebrain include the thalamus, the hypothalamus and the limbic system. The cerebrum is divided into two cerebral hemispheres connected by a mass of white matter known as the corpus callosum. Each hemisphere is divided into four lobes: frontal, parietal, occipital and temporal. The surface of each hemisphere is made up of grey matter known as the cerebral cortex and is highly folded to increase the cortical surface area available within the confines of the skull. The cortex controls perception, memory, and all higher cognitive functions, including the ability to concentrate, reason and think in abstract form. Unfolded, the highly convoluted cortex of the brain would extend over 2 square metres. Beneath the cortex is white matter, within which a number of nuclei (grey matter), known as the basal nuclei are found. The basal nuclei receive information from the cortex to regulate skeletal movement and other higher motor functions. The thalamus relays sensory information to the cerebral cortex and the hypothalamus regulates visceral functions, such as temperature, reproductive functions, eating, sleeping and the display of emotion. The limbic system is a collection of structures within the forebrain, including the amygdala hippocampus. Also known as the 'emotional brain', the limbic system is important in the formation of memories and in controlling emotions, decisions, motivation and learning.
Synapse
The gap between two neurons. Neurons communicate with each other at the synapse; electrical signals are changed to chemical signals, in the form of Neurotransmitters, which diffuse across the synapse and become electrical signals once again upon reaching the neighbouring neuron. This is known as neurotransmission at a synapse.
Limbic System
The limbic system is not a structure, but a series of nerve pathways incorporating structures deep within the temporal lobes, such as the hippocampus and the amygdala. Forming connections with the cerebral cortex, white matter and brainstem, the limbic system is involved in the control and expression of mood and emotion, in the processing and storage of recent memory, and in the control of appetite and emotional responses to food. All these functions are frequently affected in depression and the limbic system has been implicated in the pathogenesis of depression. The limbic system is also linked with parts of the neuroendocrine and autonomic nervous systems, and some psychiatric disorders, such as anxiety, are associated with both hormonal and autonomic changes. The limbic system is a collection of structures within the forebrain, including the amygdala hippocampus. Also known as the 'emotional brain', the limbic system is important in the formation of memories and in controlling emotions, decisions, motivation and learning.
Cerebrum (Forebrain)term-21
The main portion of the brain, made up of two cerebral hemispheres united by the corpus callosum, forming the largest part of the central nervous system in man. Each hemisphere is made up of the cerebral cortex and the basal nuclei, which together control all cognitive and motor function.
Nervous System
The nervous system is the part of the body that coordinates its voluntary and involuntary actions and transmits signals between different parts of its body. In most animal species it consists of two main parts, the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). The CNS contains the brain and spinal cord. The PNS consists mainly of nerves, which are enclosed bundles of the long fibers or axons, that connect the CNS to every other part of the body. The PNS includes motor neurons, mediating voluntary movement; the autonomic nervous system, comprising the sympathetic nervous system and the parasympathetic nervous system, which regulate involuntary functions, and the enteric nervous system, which functions to control the gastrointestinal system. The nervous system contains two main categories or types of cells: neurons and glial cells.
Cerebral Cortex (Forebrain)
The outer layer of grey matter, approximately 2 mm thick, covering the entire surface of the cerebral hemispheres. The cerebral cortex is made up of neuron and supporting cells (glial cells) and functions to correlate information from many sources to maintain cognitive function (all aspects of perceiving, thinking and remembering).
Soma
The soma is where the signals from the dendrites are joined and passed on. The soma and the nucleus do not play an active role in the transmission of the neural signal. Instead, these two structures serve to maintain the cell and keep the neuron functional. The support structures of the cell include mitochondria, which provide energy for the cell, and the Golgi apparatus, which packages products created by the cell and secretes them outside the cell wall.
Terminal Buttons
The terminal buttons are located at the end of the neuron and are responsible for sending the signal on to other neurons. At the end of the terminal button is a gap known as a synapse. Neurotransmitters are used to carry the signal across the synapse to other neurons.
Thalamus and Hypothalamus
The thalamus and hypothalamus are prominent internal structures. The thalamus has wide-ranging connections with the cortex and many other parts of the brain, such as the basal ganglia, hypothalamus and brainstem. It is capable of perceiving pain but not of accurately locating it. The hypothalamus has several important functions, including control of appetite, sleep patterns, sexual drive and response to anxiety. The thalamus relays sensory information to the cerebral cortex and the hypothalamus regulates visceral functions, such as temperature, reproductive functions, eating, sleeping and the display of emotion.
Cerebellum (Hindbrain)term-20
The walnut-shaped structure situated at the base of the brain. The cerebellum is responsible for motor co-ordination, posture and maintaining equilibrium.
Prefrontal Cortex
This area of the brain is thought to be involved in planning complex cognitive behaviours and in the expression of personality and appropriate social behaviour. The prefrontal cortex is found in the cortical regions of the frontal lobe which are anterior to the primary and association motor cortices. It is divided into the dorsolateral, orbitofrontal (also called the limbic frontal lobe) and mesial prefrontal areas.