Week 2. Brain Mechanisms and Behaviour I II PDF

MED 104-Medical Psychology Brain Mechanisms and Behaviour I - II Dr Stelios Georgiades, AFBP’sS, C.Psychol, Associate Professor of Clinical Psychology Dr Achilleas Pavlou...

MED 104-Medical Psychology Brain Mechanisms and Behaviour I - II Dr Stelios Georgiades, AFBP’sS, C.Psychol, Associate Professor of Clinical Psychology Dr Achilleas Pavlou, Lecturer  An Introduction to Cells and Neurons An Introduction to Biological Psychology: Biological psychology, also called physiological psychology or Behavioral Neuroscience, is the study of the physiological bases of behaviour. Biological Psychology is concerned primarily with the relationship between psychological processes and the underlying physiological events—or, in other words, the mind-body phenomenon  An Introduction to Cells and Neurons Theories of the relationship between body and mind date back at least to Aristotle who conjectured that, “the two exist as aspects of the same entity, the mind being merely one of the body’s functions”.  An Introduction to Cells and Neurons In the dualism of French philosopher René Descartes, both the mind and the soul are spiritual entities existing separately from the mechanical operations of the human body. Related to this, is the psychological parallelism theory of German philosopher Gottfried Wilhelm Leibniz. Leibniz believed that mind and body are separate but that their activities directly parallel each other.  An Introduction to Cells and Neurons In recent times behaviourists such as American psychologist John B. Watson moved away from consideration of the spiritual or mental and focused on observable human and animal behaviours and their relationship to the nervous system.  An Introduction to Cells and Neurons Based on this brief historical development of Biological Psychology, its focus today is the function of the brain and the rest of the nervous system in activities recognized as characteristic of humans and other animals. Examples: Thinking, Learning, Feeling, Sensing, Perceiving. An Introduction to Cells and Neurons The Brain An –A Introduction to Cells and Brief Gross Neurons Phenomenological Presentation. The Brain is divided into a number of different parts. Looking at the brain from the left side. This part on the top, is called the cerebrum. Cerebrum, is the biggest part of the brain. The Brain An –A Introduction to Cells and Brief Gross Neurons Phenomenological Presentation. Looking down from the top, one cannot see the parts underneath. We can only see the cerebrum that is divided into a left and a right half. These halves are called the cerebral hemispheres. And there's a left and a right cerebral hemisphere.  An Introduction to Cells and Neurons Sometimes brain structures are referred to by the names of the structure that they develop from in the embryo. The first part of the developing brain of the human embryo is called the fore brain or it has a longer name of Prosencephalon. The part behind the fore brain is called the mid brain and it also has a longer name called the Mesencephalon. The part behind the mid brain is called the hind brain which is also called the Rhombencephalon.  An Introduction to Cells and Neurons The Prosencephalon (fore brain) is going to become the cerebrum. The Mesencephalon (mid brain) is going to become the mid brain. The Rhombencephalon (hind brain) will become the rest of the brain: The pons, the medulla, and the cerebellum. Subdivisions of the Embryonic Brain  An Introduction to Cells and Neurons These are the parts of the Nervous System that make up most of the Central Nervous System (CNS). Everything in the Nervous System that's not in the CNS is in the Peripheral Nervous System (PNS). The central nervous system is called that because it's in the centre of the body and then the peripheral nervous system is called that because is in the periphery (i.e., it's going all over the rest of the body).  An Introduction to Cells and Neurons Lysosomes Gologi Aparatus Nucleus Cytoplasm Mitochondria Membrane Endoplasmic Ribosomes Formation  What distinguishes a neuron from the other cells is their shape. From the central body of the neuron a number of small fibers seem to be coming out dendrit es Terminal Buttons Soma Axon  Every branching of the neuronal axon, at the end it has a terminal button which is also called pre-synaptic end. This is the area where the neural axon releases chemical substances that go through synapsis. dendrit es Terminal Buttons Soma Synapsis Axon An Introduction to Cells and Neurons Receives Information from other neurons, consolidates information...... And sends the information to other neurons An Introduction to Cells and Neurons The messages that are sent through the axon from the body to the terminal button are called action potentials  An Introduction to Cells and Neurons The peripheral nervous system consists of two types of structures: The first are called nerves. A nerve is an enclosed (cable-like) bundle of axons in the peripheral nervous system. A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons to peripheral organs.  An Introduction to Cells and Neurons The second main structure of the peripheral nervous system are called ganglion (plural: ganglia). Ganglia are the lumps that are attached to nerves and they contain the somas of neurons.  An Introduction to Cells and Neurons The ganglia contain the somas of some of the neurons in the peripheral nervous system. Some of these axons traveling through nerves carry information in to the central nervous system from the periphery. When they do that, we call those afferent neurons. Afferent neurons carry information in to the central nervous system.  An Introduction to Cells and Neurons Neurons whose axons carry information away from the central nervous system we call efferent neurons.  An Introduction to Cells and Neurons Types of Cells in the Nervous System Most neurons can be anatomically characterized as: Unipolar or pseudounipolar: dendrite and axon emerging from same process. Bipolar: axon and single dendrite on opposite ends of the soma. Multipolar: two or more dendrites, separate from the axon. Anaxonic: where axon cannot be distinguished from dendrites. Types of Cells in the Nervous An Introduction System to Cells and Neurons  The other An Introduction main to Cells of components andthe Neurons nervous system are the neuroglia. Originally, researchers thought that the main role of neuroglia was to glue neurons together. Hence their name γλία and/or γλοία meaning glue. Neuroglia non-neuronal cells that maintain homeostasis, form myelin, and provide support and protection for neurons in the central and peripheral nervous systems. In the central nervous system, glial cells include oligodendrocytes, astrocytes, ependymal cells and microglia, and in the peripheral nervous system glial cells include Schwann cells and satellite cells. Astrocytes (also called astroglia) have numerous projections that link An Introduction to Cells and Neurons neurons to their blood supply while forming the blood-brain barrier. They regulate the external chemical environment of neurons. Oligodendrocytes produce the so-called myelin sheath. The myelin sheath provides insulation to the axon that allows electrical signals to propagate more efficiently. Ependymal cells are involved in the creation and secretion of cerebrospinal fluid (CSF) Schwann cells provide myelination to axons in the peripheral nervous system (PNS). They also have phagocytotic activity and clear cellular debris that allows for regrowth of PNS neurons Satellite Cells help regulate the external chemical environment.  An Introduction to Cells and Neurons Neuroglial are approximately, 10X smaller than neurons. In the human brain this type of cells are approximately 10X more than neurons, Therefore, in the human brain, glial cells occupy the same space/volume as neurons.  An Introduction to Cells and Neurons In most areas of the brains of vertebrates, cells can not be replaced Exceptions (until recently) Olfactory (Smell) cells Neuroglial cells More recent research on stem cells seems to suggest otherwise- especially in the area of the septohippocampal region in limbic system.  An Introduction to Cells and Neurons More than 100 years ago Paul Ehlirch discovered if a blue dye is injected into an animal’s blood stream, all tissue except the brain and the spinal cord will be tinted blue. However if the same dye is injected into the fluid filled ventricles of the brain, the blue color will spread throughout the CNS. This experiment demonstrates that a barrier exists between the blood and the fluid that surrounds the cells of the brain. This barrier is called the Blood Brain Barrier An Introduction to Cells and Neurons  An Introduction Some substances cantocross Cells andthe Neurons blood brain barrier, others cannot. Thus, it is selectively permeable. But Why do we need the blood brain barrier??  An Introduction Some substances cantocross Cells andthe Neurons blood brain barrier, others cannot. Thus, it is selectively permeable. But Why do we need the blood brain barrier?? Lack of Uniformity of Blood Brain Barrier Example the area postrema BBB is much weaker there permitting neurons in this region to detect the presence of toxic substances in the blood. A poison that enters the circulatory system from the stomach can thus stimulate this area to initiate vomiting.  An Introduction to Cells and Neurons Area Postrema of the Medulla The area postrema is a medullary structure in the brain that controls vomiting. Its privileged location in the brain also allows the area postrema to play a vital role in the control of autonomic functions by the central nervous system.  Reflex Arc Example Let’s examine the interaction of three neurons and a muscle that control the reflex of withdrawal Reflex Arc Reflex Arc Reflex Arc Reflex Arc HOW DO NEURONS COMMUNICATE? The messages that are sent through the axon from the body to the terminal button are called action potentials Synapsis  Structure and Function of Synapses Human neurons are rarely at rest and they are constantly bombarded with stimuli causing actions potentials.  Structure and Function of Synapses There is not just one nerve that travels from different parts of our body to the brain. There are many billion nerves that interact with each other passing on the message to the brain just like the telephone game. Structure and Function of Synapses Communication Between Structure and Function ofNeurons Synapses The primary means of communication between neurons is synaptic transmission. The transmission of messages from one neuron to another through a synapse. These messages are carried by neurotransmitters released by terminal buttons. These terminals diffuse across the fluid-filled gap between the terminal buttons and the membrane of the neurons with which they form synapses.  Structure and Function of Synapses As it is known synapses are junctions between the terminal buttons at the ends of the axonal branches of one neuron and the membrane of another. Synapses can occur in three places: on dendrites, on the soma and on other axons. These synapses are referred as axodendritic, axosomatic or axoaxonic (although the most common one found in the Nervous system is the axodendritic). Structure and Function of Synapses  Structure and Function of Synapses The presynaptic membrane, located at the end of the terminal faces the postsynaptic membrane located on the neuron that receives the message (the postsynaptic neuron). These two membranes face each other across the synaptic cleft. A gap that varies in size from synapse to synapse but the average distance is 1nm (1 billionth of a metre). The synaptic cleft contains extracellular fluid through which the transmitter diffuses. The cytoplasm of the terminal button contains small synaptic vesicles, small rounded objects in the shape of spheres or ovoids.  Structure and Function of Synapses These vesicles (=little bladders) are found in large numbers around the part of the presynaptic membrane that faces the synaptic cleft – next to the release zone, the region from which neurotransmitter is released. Synaptic vesicles are produced in the soma and are carried by fast axoplasmic transport to the terminal buttons. Structure and Function of Synapses Structure and Function of Synapses  Structure and Function of Synapses Currently, more than 100 neurotransmitters have been identified. Seven of the most important are summarized in the table below:  The Nervous System A human nervous system is divided into two main parts. The Central Nervous System and the Peripheral Nervous System  The Central Nervous System The Central Nervous System or CNS consists of the brain and spinal cord. It is responsible for processing information gathering from the rest of the nerves and transmitting instructions to the body. The Peripheral Nervous System (PNS) includes all other nerve pathways outside the brain and the spinal cord.  Reflexes There are several types of reflexes that travel through the spinal cord. This sort of reflexes control heart muscles, glands and organs.  Reflexes Somatic reflexes control involuntary movement and skeletal muscles.  Reflexes There are many innate reflexes, which are inherent from birth, but the development of some reflexive responses can be influenced by learning and repetition. They are typically mediated by the spinal cord, though the brain remains the orchestrator of the nervous system, overseeing numerous motor functions and reactions.  The Brain The brain is the source of all our behaviours, thoughts, feelings and experiences. It is the most complex organ in the human body and perhaps the most remarkable.  The Brain The forebrain, the midbrain and the hindbrain  The forebrain consists of the cerebrum, the thalamus and the hypothalamus. All are parts of the limbic system.  The Brain The midbrain consists of the tegtum and tegmentum. The hindbrain consists of the cerebellum, pons and the medulla. Often the midbrain, pons and the medulla are referred together as the brainstem. The Brain  The Brain The cerebrum or cortex is the largest part of the human brain and is associated with higher brain functions such as thought and actions.  The Brain The cerebrum cortex is divided into four section called lobes. The frontal lobe The parietal lobe The occipital lobe and The temporal lobe.  The Brain The frontal lobe is responsible for Reasoning Planning Parts of speech Movements Emotions and Problem solving.  The Brain The parietal lobe, controls movement, orientation and recognition  The Brain The occipital lobe is associated with visual perception processing  The Brain The temporal lobe helps control perception recognition of auditory stimuli, memory and speech  The Brain The cerebral cortex looks very wrinkled. This makes the brain more efficient because it can increase the surface area of the brain and the amount of neurons within it.  The Brain A deep crack divides the cerebrum into two halves known as the left and the right hemispheres. The two hemispheres look mostly symmetrical yet it has been shown that each side functions slightly different than the other. The right hemisphere has to do with creativity and the left hemisphere is associated with logical abilities.  The Brain The corpus callosum is a bundle of axons which connects these two hemispheres The Brain The cerebellum, or little brain is similar to the cerebrum because it has two hemispheres and it has a highly folded surface called cortex. This structure helps with the regulation and coordination of movement, posture and balance.  The Brain The limbic system often referred to as the emotional brain is found deep within the cerebrum.  The Brain This system contains the thalamus, the hypothalamus, the amygdala and the hippocampus.  The Brain The thalamus is a massive gray matter located in the forebrain. The thalamus is the relay station or gateway for sensory information such as touch, taste, hearing and vision (with the exception of olfaction!) to different areas of the cerebral cortex This includes relaying pain signals to the cortex, where the conscious perception of pain occurs.  The Brain The hypothalamus’ function is to regulate homeostasis, emotion, thirst, hunger and the control of the autonomic nervous system.  The Brain The amygdala is part of the telencephalon located in the temporal lobe and is involved in memory emotion and fear.  The Brain The final portion of the limbic system is the hippocampus. This part of our brain is important for learning, memory and converting short term memory to more long term memory.  The Brain Underneath the limbic system is the brain stem. This structure is responsible for basic vital life functions such as breathing, heart beat and blood pressure.  The Brain This is the most simple part of the human brain because animals’ entire brain such as reptiles resemble our brain stem.  The Brain The midbrain is part of the brain stem and it includes the tectum and tegmentum. It is involved in functions such as, vision, hearing, eye movement and body movement. The medulla oblongata and the pons have centres of vital functions such as breathing and heart beat.  The Brain The brain is small and yet an extraordinary organ in the body. The design and processes that it can carry out is a work of art that we only know a fraction about.  The Brain Over the last ten to twenty years huge breakthroughs in research have shed light on different functions of the brain but there still so much to discover. The integration of nerve cells and bundles in our brain is likely the most complex and amazing part of the body.  The Brain Together billions of our nerves collaborate to give the depth of our human experience including emotion, processing information, memory and new ideas.